[Cannot open files that I created today]

EDIT: Nevermind, turns out my thumb drive was corrupting all my files. 

Hello,

I created several files earlier today on Affinity Designer. I tried to reopen one of them a few hours later, and I keep getting the error "The file type is not supported" (see attached pic). What could be causing this? I was literally accessing it a few hours ago with no issues. 

• I am using Windows 10
• Updated Designer to the most current version (1.8.4) hoping it would help (it didn't)
• Restarted computer
• Held down CTRL while opening to reset defaults
• I just created a new document and saved it to test if I could open new files. It opened successfully.

So I don't know what happened or how to fix this. I really need these files for work. Thank you!