Determine with a non contact voltage detector from hd
I was able to find the capped black wire from information from y'all! I started snooping and found it. When I touched it to a known hot wire the light that was the original problem came on.
Pen testers have their place but in this case you need to use a volt/ohm meter to test with. The pen tester you are using can pick up induced voltage and give confusing readings.
If the closet light you mentioned is the same one that quit working (as you mentioned in post three) then you need to troubleshoot that circuit out more. Hooking this circuit into another one that had a different power source could cause serious problems.