Looks like Gek0 is probably most correct. The bills dribbled in over a year in ammounts small enough not to trigger the screens my office uses to protect my family from fraud. Even with that, some alarm bells should have gone off when a $12K bill for a new air conditioner came in.
I still have a hard time believing the ex was actively trying to screw with me. When we were together, there were some problems that I attributed to psychological issues. In retrospect I wonder if it might have been early onset of age related declines that the daughter in law took advantage of.
Regardless, my side is pissed. I've got to talk with a family law lawyer and take steps to make sure the ex can't bind me in any further contracts.