I've never actually used DM for sync, but I have used device switch. DM creates a backup before it does a lot of things, I'm not 100% sure about sync though.
There is a chance it created one, and in my experience it puts them in your My Documents folder (not sure if it creates a sub-folder) and it would be a .ipd file.
I know that may not be much help, but it's a place to start.
i did the same thing with my pics...
even thou i backed up my phone... the pictures are no where to be found
Pictures are probably stored on your media card. I don't think they would be a part of the DM backup file. I think you would have to back them up separately.