I am talking about Boris Rozhin's livejournal ('colonelcassad'). That's about as close as it gets to rebels' mouthpiece, being probably the most popular social media outlet with separatist viewpoint (not to be confused with Russian govt's viewpoint). Of course he is not an official figure of any kind, but if anyone can be trusted to be able to tell legit sources from 'hotheads in their mommies' basements', that's him.

It's a journalist from Crimea, Nobody you should consider to be fully informed with what rebels do. I can imagine he's now a kind of a war reporter, but in wars there are a lot of rumors. Nothing can be more probable than that somebody actually saw the crash and produced the rumor that that's an achievement of the rebels and the journalist repeated it.