I remember back in the days of vinyl that the 7" UK picture sleeve of XTC's first UK single 'Science Friction' was a holy grail for many collectors, only I'm not sure if it ever actually existed. I got told by a dealer that although the 12" picture sleeve was common the 7" picture sleeve had only ever been rumoured to exist. I don't know if it was ever proven to exist or not... At same time I was told by a dealer of the existence of a European 7" of The Tubes 'Poland Whole' and as a collector at the time (pre-internet) I spent years looking for one of those along with a promo copy of The Tubes live album with a booklet of cuttings. As far as I know, with all the on-line resources available now, neither of these items ever existed. On a similar note a friend of mine who was a big Jean-Michel Jarre collector in the late 80's phoned a big dealer at the time and enquired about an album which he knew didn't exist purely to try and create such a phenomena. The album was constantly listed as a 'Wanted' item in the shops adverts for years after, despite being fictitious. It'd be interesting to know if collectors are still unsure about it's existence. So, what holy grails have you searched for fruitlessly before discovering they never even existed in the first place?