Originally Posted by
Fly AA J all the way
I would email UA and tell them you found something in the seat pocket, you would like to return it to its rightful owner and that they should pass your contact info on to anyone who calls them claiming to have left something in the seat pocket. If, after say, a month nobody calls you, keep it. But I say better you than a UA employee.
This is by far the most sensible, suggestion so far.
However my personal technique: look left, look right make sure there are no witnesses and then introduce mr wallet to mr pocket.