I'm sure this might have been covered at some point, but i haven't found information with salution to my problem.

Bought Diablo played for 1 or more hour the first day. Saved the game went to back next day, lauched the game and noticed that my character wasn't there. I though i didn't save maybe started a new character. Came back to it druing the day couple times between things i had to do. Day 2 played for total of 4 or so hours. Yet again went to bed next day launch game the save is gone.
I have the entire steam library on this harddrive every save works no problem and there is plenty of space.
Can someone tell me what is going on or where to find my save file?

Thank you for all the help in advance.

Character files are normally written to the game's installation directory, with a file extension of .sv. The game should find and show them automatically if they were put there, though. I heard of one person who experienced crashes during saving, and lost his save file as a result. I haven't heard of anyone who saved successfully, then later had the saved file disappear.

If you start a game, save it, quit the program, and immediately go looking for the save file, can you find it? That is, are the files never being saved, or are they saved and then vanish before you come back for your next play session?

The issue could be that you do not have write access to the install folder and the system is overlaying another folder for writes, some clean up tool could then be removing this overlay folder. You can try running the game in admin mode or try a modern port like DevilutionX https://github.com/diasurgical/devilutionX/releases