I've often thought we needed a word to describe someone (usually famous) dying whom, until you heard the sad news, you wrongly believed died years ago. From now on, I'm going to call it ‘bilking’ (as in ‘Acker has bilked’).
Postscript (04-Nov-2014): Damn! I just told Jen my cool new word, and she immediately pointed out that to bilk is already a verb, meaning to defraud or evade (as in ‘to bilk paying one's bill at a restaurant’). But I reckon carrying on living for years when other people think you're dead is a form of evasion, so I'm sticking with my neologism.
I think I prefer 'ackered'!
‘Ackered’ sounds more like Cockney rhyming slang. If ‘Acker Bilk’ is milk, ‘ackered’ would mean milked.