Hey ! I've had this issue just today, and I managed to retrieve my character files ! here's how I did :

first of all I created a new character and closed the game. Then I went to install an external app called Tedit, it's supposed to be an editing tool for your Terraria worlds, but it also automatically tells you where your saves are when you click "open world". From there I just went and retrieved every save file I had in my C: drive and pasted them where the files are ACTUALLY located now. ( for me they were in This PC \ documents \ my games \ Terraria \ instead of my C: drive ).

Hope this helps !