All pictures disappeared. DATA remains
 

I have the data file with all my pictures, and thumbs, medium etc. However, photopost thinks there are no pictures since I tried to rescan the database and rebuild thumbs. Is there any way to get that info back? Or are the pictures gone forever, even if they are in the Data folders?

Not without a mysql backup of your photopost tables which is why upgrade instruction state to backup your database before any upgrade.