I just finished this film, and the thumb drive issue is one of several questions that arose for me. I can't understand why they would count on her not noticing it was inserted in her computer. Considering how reclusive and paranoid she was, she would have been keenly aware of anything being even slightly out of place in her apartment.
And then, how about the whole, silly, elaborate plan to begin with, to where murder had to be involved? Ray was the obvious puppet master behind it all. Somehow he was able to make her immense fortune disappear along with her true identity, and then relocate it under her alias, with at least a sizable amount of it in her family owned bank no less. If he was smart enough to do all of that, he could have easily milked her wealth steadily over a 17 year period, amassed a fortune of his own without anyone being the wiser, and it would have been in addition to his own income as a very successful doctor. The one thing that makes sense about his motivation is that he was obviously very burdened with her. Speaking of 17 years, and the fact that she was still being sought, as evidenced by the importance of the media in the story, it seems that at some point, authorities would have called in at least one, if not a team of good forensic accountants, who would have uncovered Ray's obfuscation of her finances in an expedient manner. But then we wouldn't have, as we all sometimes surmise, this movie, correct? ;)