When I locally modify a file and then git revert it from the IDE before the file is saved(!), then file does revert on disk but in the IDE cache the modified version stays. Closing and re-opening the file shows the modified version, closing and relaunching RubyMine has the same effect (i.e. it shows the locally modified file, in memory buffer or something.)
The only way to get RubyMine out of this is to make another modification to the file, hit Save, then revert.