If the company had to decide between loosing thousands of dollars every time this happens or have some process of tracking / taking notes / assuring quality of the process- believe me- the company would change their behavior. But in this case, there is no risk to the airline- they will just make the customer eat it.
I mean, losing your bag sucks, but it's a weird case: how many times a year do you think that someone takes the wrong bag, then takes the effort to call American and let them know, but then fails to actually return the bag?
And it's hardly a case for interpol, either. "Check the call logs"? Yeah, Lebowski, they got four more detectives working the case, in shifts.