If the "Search for" field in "Find in files" is empty, then "Find File" doesn't work.
Enter anything into this box, switch back to FindFile, and now it works.
Also, I could swear I was using FindFile and had several searches not find what I was looking for.
Then I noticed in the search output that the results shows "Find all" instead of "Find files".
Could be user error, but I don't think so.
So far, no repro.