Did he overwrite your saves with his? If so, you likely can't recover them unless you happened to have backups somewhere or have file history running for the save files. Just to be double sure, though, copy-paste "%userprofile%\Saved Games\CD Projekt Red\Cyberpunk 2077" (without the quotes) into the address bar in explorer/file explorer and check to see if your saves are still there.

I hope you can find them but either way, I highly, highly recommend backing up your game saves independently of cloud sync. Cloud syncing for saves is more so you don't have to port your saves over across all your devices, it's not particularly meant to be a means of storing/backing up your save files. Even uploading them to something like Dropbox (keep it private, of course, unless you want to share your saves with a friend) should work but I always prefer physical storage such as an external hard drive or even a USB flash drive or SD card.