There is no file named that in our Photopost code and never was.
I would suggest you check out mod sites for whatever hack or mod you have installed on your site
There use to be a hack called the thumbnailer which was written for OLDER photoposts and use to be posted on the photopostdev.com site and you may find that posted here on this site but dont know what is there or not
http://www.photopost.com/forum/photopost-pro-mod-corner/