Actually, you can probably soak the photo in water. When it is soaked through, remove the paper that is stuck. The photo can then be air dried or dried with a hairdryer. There is a very good possibility that the photo will have a tendency to curl afterwards though.
I worked for a printing company and rinsing photos with water is part of the printing process.
If this is a computer-printed photo done with printer ink, the water will only damage it further.