When you saved first in 1.17, you were asked to rename or overwrite. If you chose overwrite, sort out your map in 1.17 or start new - or send the bugsplat the game generates and wait for an answer from the developer, should he see a way and wants to analyze your save.

If you chose rename, there is a save of the same name added OLD to the file name. That is your 1.16 save.