Contacts disappeared from Desktop on Palm Pilot Desktop?

My palm pilot was stolen so I rely on my desktop. Suddenly, all of my contacts have disappeared, but my memos, notes, etc are still there. I tried to reload archived contacts however the file it is looking for is *.aca. I found several older versions, but the Palm desktop says they are invalid. I also tried to look for back up files and the desktop also says these are invalid. My settings say that backup is set for every 15 minutes. Where is it and how can I get it reconnected to my desktop?