While they are fighting Julia demands to be paid and Richard throws her money on top of his jacket on the bed. The next shot of the money shows it neatly next the the jacket and the jacket is now folded.
Actually there are numerous slipups in this movie, such as the amazing reappearing/disappearing sorbet glass in front of Richard Gere in the fancy restaurant, and the fact that in one scene Julia Roberts removes his shoes and socks in a park and a split second later he is reading to her fully shod. (And yes, I realize full well these insights are not original to me.)
Read to her? The next scene after the park is them riding horses. Most of the things up here aren't even slip-ups. People just need to watch a little closer next time. The sorbet glass does disappear. But the shoes thing doesn't happen, the money doesn't move, she never took it, not touched it so how could it have moved?
I don't think the shoes in the park thig is really a slip-up because it was showing how they spent the whole day together so when she took his shoes off it could have been a couple of hourse later when he put them back on again.