since a few weeks (maybe since updated from 7 to 8?) the "find in path" function doesn't find anything, just show "No occurrences of ...". Today i was really pissed... So i looked around about such topics and found the solution here "https://devnet.jetbrains.com/message/5508561#5508561" (File | invalidate caches and restart). This issue is maybe related to this question "https://devnet.jetbrains.com/message/5484119#5484119" and maybe many more concerning the "find" functionalities.
Invalidating the cache means also losing the local history. Is there a solution without losing the history?