Drill/Driver - Where Does The Red Wire Go?

I've got an older Black & Decker variable speed electric drill, that I just recently had to replace the brushes on. That all went pretty well, and the drill parts all came back together just fine.

When I went to close up the back plate, I noticed that a single red wire had apparently come loose from its contact. Despite looking for a long, long, long time - I just can't seem to locate where this red wire connects to the drill circuitry. From the pictures, the position and the length of the wire suggests the likely general location of its contact, but I just can't seem to find it. I wonder whether this wire might be a lead to the variable speed trigger, but again - no visibly apparent contact to insert the wire into. Based on the uber straight condition of the bare end of the red wire, it appears as thought the wire went in an insertion contact, and not some kind crimp contact like the leads to the brushes.

Any thoughts or suggestions based on this description, or the attached pictures.