I think that is very likely what happened, and now that it's several years later, I'm pretty much over it, and I doubt it will ever be truly explained. At the time, though, I really wanted it to be a specific person. Part of me hoped that it was River that caused the explosion, perhaps unaware she was doing it as part of her evil programming. She was the only one onboard, afterall.
That's what I like to think. Whether or not that was in Moffat's head at the time, it ties up very nicely. There's certainly nothing to disprove it.
What I'd have liked to see explained was the eerie silence falling over the Venetian market, with the populace disappearing suddenly...