Originally Posted by
Paolo01
Mail it to the DOS. They will cancel it (Final flag) and return it to you. It will most likely have two holes in it when you receive it, but you will still be able to see all of the stamps.
Very consistent and accurate advice being given here. When you asked for a new passport, your old one would have been added to DoS and Interpol databases of stolen and lost travel documents. Unfortunately not all countries routinely ping Interpol when someone crosses the border. For that reason, if your "found" ppt was to be in the hands of criminal, they would have a real, live, valid US ppt to use as they see fit. Having your "found" ppt properly cancelled would avoid this. Also, it's never good to have a lost ppt on your record at DoS. If you were to lose two, they might put restrictions on your next ppt (e.g. issue for less validity than 10 years).
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13F