I have noticed it mainly with pagefile.sys
It shows if I rebuild the cache, or reindex, or reinstall the program. But then I don't know why it vanishes from the results, and never reappears unless I do what I stated earlier. Here you can see it at the top of the results.

Then it randomly stops to show

I'm obviously not excluding it or something, it happens even after I reinstalled the program (deleted all my data and configs as well).
I don't know if it also happens with other files, probably not since the items listed in the program just went down by one. It started with 1364a, previously on 1363a it was fine. I noticed it since I use the program a lot (very useful!)