I have no experience what so ever with your problem, but aren't you afraid that, if you just keep it wet on the area that sticks, you'll get distortions in the paper after drying? The paper might stretch and shrink unevenly or leave drying marks around the wet spot.
And if it is like FB paper, this could be even worse?
I think I would try one photo at first: the one best scanned and most unimportant if lost. Or the one with a small sticking area at a corner.
Or - even better - on a similar photo that isn't sticking at all, but you don't want to keep anyway. Tape it to a sheet of glass and try some water with PFlo just on a small area and keep it wet. Then dry and see what happens.
Let us know how it worked out!