No, it's people like you who believe the rumor that won't "let them drop it". No, really; the moment the event even comes up in a conversation, the believers are all over it, demanding belief in it like it's their mission to convert the unbeliever to it. At least, that's usually how it turns out, whenever I see it brought up. The believers are usually the ones that are more vehement about this topic than the unbelievers or those who don't care, either way.
You're not getting what I'm saying about the flyers; the announcement would be for the chance to PLAY AGAINST IT, NOT for its release. Again, it would be like someone confirming they displayed their Babe Ruth rookie card at the Baseball Hall of Fame, but no flyers announcing the event showing up; the flyer isn't announcing the chance to GET the rookie card, only to SEE it, and if it was a big enough deal for rumors about it to circulate, then surely there SHOULD'VE been SOME announcement about it. If I confirmed a rumor that I got to see Kelly Clarkson in concert at the state fair a few years ago, but a search into the events calender of the fair for the year it supposedly happened didn't come up with anything, would you still believe that I actually saw her? No, you wouldn't, and why? Because, despite Kelly Clarkson in concert being a really big deal, especially if it happened during a big event like a state fair, there was no announcement for it. Same thing, here; being able to duel against the Seal would be a huge deal, even if you don't win it as a prize, and you'd think that either UDE or GenCon would announce it, but neither of them did, so how can I believe that it actually happened?
You are allowed to take pictures of GenCon and YGO tournaments, otherwise videos like
wouldn't have been made. Fan photos and videos of GenCon and Regionals have been circulating through the internet for years, so if this was an actual event, there would be some visual evidence of it.
I already mentioned why they would set up the rumor; they were at odds with Konami, and wanted more of the fans on their side. What better way of doing that then to hype up one of their achievements? Them spreading this rumor to make themselves look better than Konami to draw interest away from Konami to them is perfectly within line of what we know of their practices, and it seems to have worked; a good deal of the people I've talked to on UDE's forum and elsewhere who believes the rumors are diehard UDE supporters, which was probably their goal; trick people into believing a fabrication of theirs that makes them look superior than Konami, and gain more followers as a result.
Also, didn't they give away a replica of the Millennium Puzzle as a prize during one World Championship tournament? The analogy you're making isn't working, in that case, especially since the Seal has a definite effect that anyone who watched the show could verify if they saw it, an effect that CAN translate to the real world game. It doesn't matter if it was just a prop, it supposedly existed AND WAS PLAYED at the GenCon Duel the Master, so SOMEONE should've seen it and been able to confirm both its existence and the duel. No one can; no one has pictures, no one has video, no one has flyers announcing the chance to duel against it, NOTHING. There is NO EVIDENCE WHATSOEVER that the event OR the card happened.
Also, your analogy about "just because I don't have anything to prove I went to Disney doesn't mean I didn't" is stupid, because that's exactly the point I was trying to make; how can anyone believe that you went to Disneyland or Disney World if you have no pictures or video, no receipts, nor memorabilia, no souvenirs, nor flyers or pamphlets proving that you went there? I can't just take your word for it; if you vanish for a few weeks, come back, and say you went to a specific place, but you provide no evidence verifying your claim, and I can't find any evidence to prove you did go there, then how can I be sure you DID go there? Blind faith? If you were my teacher, and I told you I did an assignment and I should get an "A" in it, but I don't produce a single thing that shows that I actually DID it - no paperwork, no notes, no photos or video showing off the assignment, not even an audio recording of me rehearsing the assignment - would you believe me? No, you wouldn't; you'd assume I didn't do it, nail me with an F, and force me to do it all over again. Even UFO sightings and claims about Bigfoot and the Loch Ness Monster has SOME visual evidence to back up their claims, as unclear and sketchy as they may be. But this? Not even a whisper of evidence.
It seems to me like you guys are keeping the rumor alive by believing in it, not me for trying to disprove it. You rationalize why there isn't any evidence to back it up, coddle UDE's silence on the matter as a potential security risk (which is stupid, especially if it was "just a prop that was thrown out" as you say it was; why bother protecting a piece of cardboard that couldn't even be passed off as a real card, in the first place?), and encourage other people to blindly accept that the card and the event is real as is rumored without trying to check up on its veracity. That gives credence to my belief that UDE started the rumor in an attempt to gain more followers; it obviously worked, since you're unwilling to NOT trust their word on this, despite all of the lies and exaggerations they've given in the past. And what about GenCon? Surely they don't follow the same standards as UDE when it comes to this rumor; UDE was their GUEST there, and if they wanted to, they could cancel their booth and events at any time. If ANYONE would have any evidence that the duel against the Seal was real, THEY would have it, but not even THEY do. Just to make sure, I'm emailing them with this question, right now, so we'll see what they say, though I doubt they'll confirm it.
EDIT: I was right; they said they "weren't privy to that information", and thus couldn't confirm it. Things get more and more suspicious, and further bend towards the rumors being fake than true. I'm sorry, but with only the rumor to prove that it's real, I've got to call it: it's not, it never was, UDE was just screwing with us to garner more interest in themselves and steal fans from Konami at the time.