If your using the right script here it doesnt do anything to photos but place the right userid onto them. It deletes no photos.
Just like any upgrade or import your suppose to make backups before running them.
I would tend to think your no photos is because of something else you ran not this specific script. I used this very script when I switched from UbbThreads to VB
as did Michael.
What other steps did you do here besides run this script. Did you try to run this script on an old version of Photopost say 4.8 then do a photopost upgrade? That would not work. This script is for 5.0 and above. So it is very important to know what you did to cause this to be able to suggest a resolution.