Deleted files from hard drive by accident when time machine asked to back up

Hi, Yes your chances of recovery are quite high.

I suggest you dont back up anything to the passport until you have had a chance to run some scans on it using some free or trial recovery software on your computer.    You don’t see the files on your passport right now but they are still there. They are just marked for deletion. They should reveal themselves with the recovery software you use. Good luck!