I listened to it but don't recognise it. Maybe someone else will.
It doesn't sound like any classical piece I've heard. There was one small part, right at the beginning, where it sounded like a Turlough O'Carolan tune (Irish harper, 1700's) but then it wasn't the tune I thought it would be.
The thing about O'Carolan's music is that the tunes are deceptively simple, but really well crafted with beautiful tunes. There are a lot of his tunes I don't know, so it is a possibility. I'll listen again and see if it rings any bells.
Does your friend know any of the other tunes on the tape. Maybe we can track it down by searching for tune titles on some of the CD sites - if it is a commercial tape, and not a guitarist taping his/her own performance at home. Then you'd have little chance of finding it.
Good luck in your search.