You had some nice ideas in there but this just doesn't seem practical or workable in the real world. There is a very low chance the spectator would leave something that was in their pocket behind for you to take. It is also important to remember that the main things people carry in their pockets are cell phones and wallets. Things like these have value and in some cases personal attachment to the spectator.
I can picture more of an annoyed reaction as opposed to a mystified one. It would be like stealing someone's wallet that they left on a table and keeping it with you for several hours (as you recommended) before returning it to them. I guess my main feeling with this is that you should be careful because the spectator may not perceive it as magic...
Now other people may think differently but these are just my thoughts. You do have some nice ideas though so keep it up!
You're missing the point. This essay isn't all about the method of this little piece of magic. It's more about the feeling behind your magic and the effort put into your magic. I feel that the idea of the left behind object is more of a side note to those of establishing yourself with beleivable magic prior to doing something that may take a little more faith to beleive as real magic. And that of beleiving the magic yourself so that you will inspire belief in the spectator.
Also it would be a good lesson to not just look at things as they are on the surface, as you did with this essay while just consentrating on the trick part of the effect when there was so much more in the text. Remember this, A lot of amateur magicians don't realize the effect that they have on an audience. If you perform this particular illusion well then they would have no reason to think that you stole their wallet and kept it with you for several hours.
Just some stuff to think about.