Apex 300bhs bathroom fan wiring

[CubsFan]

We recently acquired a 2018 Apex 300bhs and installed a new Maxxair fan in the bathroom to replace the original. After lifting the original fan out of the opening and cutting the black and white wires to the fan, I tested the two cut leads to determine polarity. I discovered that there was no voltage in the wire coming from the blue wire splice, which is the positive lead. As I was gently pulling on the blue wire to test a second time, the wire came out of the ceiling with a half inch stripped on the end. The wire was about 4 feet long. Not sure what it was connected to, but whatever it was is well inside the ceiling or wall.

I really do not need the blue lead, as I spliced into the green positive lead going to the bathroom ceiling light. Both the light and the fan work great. However, what to do about the phantom connection is my issue. I have not discovered any lights, etc. that are not working due to a broken connection.

I am not too excited about doing damage to trace the wire connection. There is a blue wire of similar size and color going into the fuse panel. I have not tried to trace that as yet as it very firmly attached to a bundle going into the fall between the bath and dinette.

Anyone have experience with the bathroom fan wiring?