It's some years since I got involved with copyright. But, the rule used to be that copyright was vested in the
owner of the film. For this reason, newspapers would supply the film for their photographers and could then claim copyright. How this works with digital, I don't know, but I would guess the same applies and it would be the owner of the memory card.
What you have are prints which does not entitle you to make copies.
However, if you make inquiries at the last known address and get no response (which, of course, you won't), it could be reasonably inferred that the original owner is no longer exercising his copyright.