I had a similar install a few years ago. I got a break. The upstairs closet was carpet over subfloor. I sent my wire down thru the wall from the attic. Then I carefully remover and saved the base, cut the drywall behind the base, drilled thru the bottom plate and subfloor to the joist space. Then I peeled the carpet back and drilled (2) 1" holse thru the subfloor. One to use as a peephole and one to stick my extension bit into to drill thru the plates below. I got lucky and didn't destroy anything. I put the carpet back, kickplated the wall, put the base back and my customer was happy. Good luck.
