Windows Loaded game on steam, 300 hours lost!

[AshnotAshe]

Hey, me and my friend love stardew but we ran into a trouble, launched their game on steam and their save file of over 300 hours is just gone! We resynced their steam files and even redownloaded it to see if it could be a visual glitch. is there anyway someone can help! Anyone ran into this before??
V 1.5.6
a single player world too