I dont think in any version of Photopost if you moved an image the url would not change. If you move it it is moved
EXAMPLE
http://www.domain.com/photopost/data/502/image.jpg
you move it to cat 505
http://www.domain.com/photopost/data/505/image.jpg
The url has always changed from my recollection. I have owned Photopost php since it came out years ago and this has always been the case.