Frustrated Boston Terrier Mother

Hi,!

My 6 yr old BT, Pepper, has been urinating occasionally on one specific area rug in the living room. Of course, it is my most expensive. (We looked elsewhere, and didn't find any traces of a mishap around the rest of the house.)We discovered it about 6 months ago, and tried every pet odor remover and cleaner on the market. Eventually, we brought it to a rug cleaner and had it professionally taken care of. More disconcerting than this, is the fact that after the cleaned rug was placed in it's original spot, we noticed she urinated again. The funny thing is we purposely (and now thankfully) kept the plastic cover that was wrapped around the rug, on top, just in case. We were surprised she pee'd on the plastic. She rec'd a scolding, and knows better. She has a clean bill of health from the vet. It seems to happen when we are home, which is odd since she has constant access to the outdoors during that time. We love her dearly, she is so good and smart in every way. If anyone can provide some direction, it will be greatly appreciated. Thank you.