I hardly believe they can/will keep your money when you have received the "You sold an auction" email. If you received a "Auction in review" email, it can still be cancelled for whatever reason though.
Weird thing though is that I just received several emails with auctions in review with different amounts of gold which exceeds 200+ mil.
I've only received one email stating I've sold 160 mill though (after review)(and it's the only gold I've had on RMAH and it's the amount which shows up on the completed tabs in-game).
Not sure if I should contact Blizzard about this though.