Misplaced friends
I'm going to have to assume a few things here. You are the GM of a game and accidentally removed some players?
If so, I'm guessing they submitted RTJs (or how would you have known to add them?) so you could go back through the list of players who've submitted and find them that way. Although I haven't tested this, even if you've deleted the PM they should still show up in that list... hopefully.
If it's any other scenario, then this is probably your best bet.