Did you switch Windows users? That would create a new set of profiles in the applicable user account's My Documents folder.
In that case you can copy the saves over from the other c:\Users\<UserName>\My Documents\Larian Studios\Divinity Original Sin 2\PlayerProfiles\<ProfileName>\Savegames' folder.
Are you shutting down all non-essential programs (especially anti-virus) before starting the game?
A couple of people have had profiles disappear each time they restarted the game, caused by Comodo Cloud Antivirus (can be installed as part of a browser download) creating a sandbox for the game's My Documents folder, and saving each session separately to different folders in a c:\CCAV folder. Each time the game restarted, CCAV would create a new sandbox, so the game wouldn't see the previous profile(s) or saves.
You can try searching your hard drive for *.lsv files, in case the profile got moved somehow.
I don't suppose you have an automated nightly backup of your My Documents folder set up?
Do you have Windows shadow copies enabled, if applicable? Try right clicking PlayerProfiles folder, select Properties and (if available) switch to the Previous Versions tab to see if there are any previous copies.
https://en.wikipedia.org/wiki/Shadow_CopyYou can try a file recovery program such as Recuva, but it may not be able to completely restore a save, especially since the quick and auto saves are repeatedly overwritten. In general, the more you use the computer after files are deleted, the less likely they will be recoverable.
https://www.piriform.com/recuva