Not that 2 million is a joke, but how far and for how long can you run on that? And is it worth the risk. Now on the other hand if it's a lot more like say 30 million it would be even more tempting, but then if you get caught you're in even bigger shit becasue you know they aren't just going to be like... Oh we lost 30 million... do biggie. Nope they will hunt your ass down for that amount. So I guess in this format NO I would let the bank no of their error and hope they reward me some other way.
Now like metioned above, if it was some large amount of cash that found it's way to me. HELL's yes I would keep that!