I guess you did not find the pin in your mothers car?
For some odd reason I have a feeling that a Mexican looking guy around 40 y/o has your pin. He is in a service/cleaning job and might have some facial defect (scar or sign of previously broken nose)
The immediate feeling is that is was removed from the car, but could also have been found at the museum. Try to put up a reward for returning the pin.
I can't promise you that this info is correct in any way, but I may as well tell you my gut feeling on this