I don't have my notes with me, but I believe the 20 went to Honesdale and then back to Gloversville before permanently leaving the FJ&G. It was also on the CNYK for a while but, again, I think it then came back to Gloversville.
I would suspect rather that one of the engines was turned at Little Ferry. There are photos somewhere of one of the FJ&G switchers on or near the turntable or roundhouse in Little Ferry. Also note that the front end of one of the FJ&G engines (radiator and pilot) were removed and placed on NYS&W #206 (or so I've been told). Perhaps that would form a rationale for the turning — the engine had to point a certain way in the roundhouse so that the parts could be stripped.
I think the parts came off #21; the question is when and how
often. There is a chance it or both of the FJ&G engines were pillaged for parts more than once.
Or perhaps it was turned on the CNYK after leaving Gloversville permanently. It theoretically could have been turned at Richfield Jct. on the wye. I don't have the photos in front of me to suggest when it was there and when it wasn't.