Tons of people have experienced this exact same issue. It’s confusing when I have files in a folder but UE4 pretends they don’t exist - even UE4-specific file extensions like uasset. I am using the exact same engine version I created the project in, so how can I get them to show up?
I had this issue when I deleted a file from the UE4 content browser. I usually, delete these files manually from the explorer.
But yeah!, I’d like to know about the reason & how to stop this behavior if possible.
Generally speaking it only happens on corrupt files or with engine version mismatch (outdated files tagged for the previous engine version).