So when I had this issue, I ordered an OTG drive … I cannot actually remember if I lost much, I think I found a solution within the device - I did not be too quick to reformat the SD card, or I would have lost more!
Worth reading this thread too All photos and videos are gone, as lack of “Use Storage Access Framework” compounds the problem.
Good luck 
Edit, another post reminded me that you mentioned you were quite new to /e/…
Do you have an /e/ account?
The way that photos get synced (and reappear) can be disconcerting!