Deb,
This has been discussed several times in the recent past. Do a <u>search</u> at the top of this page.
I hate to be discouraging, but when I have tried to soak a stuck photo in a pan of cold water, it took several days of gently rocking the glass to finally “float” the photo free but the emulsion turned to jello after that time. The photo was ruined. If you try a test tug at the photo before it is completely free, you will most certainly tear the emulsion.
Some people have suggested that you pop the glass/photo into the ‘fridge for a few hours, but that hasn’t worked for me, either.
Scanning the photo through the glass seems like the best alternative, but you will probably have to do some clever Photoshopping to get rid of the “glaze” where the emulsion is in contact with the glass.