some kind of stamp on his passport that will help him reenter US?
He needs to contact the US consulate where he is located. The consulate will likely confirm his status and put a stamp in his passport or give him parol to enter into the 'usa and apply for a replacement.
I have 33 years experience and practice immigration law only. My answer to your question is general in nature and not to be construed as legal advise or as establishing an attorney-client relationship. For additional discussion regarding your personal situation a scheduled consultation is required.
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