Where did the child support back payments taken from taxes go?

My ex husband recently informed me that after he filed taxes last year they took out over 1,000 as part of his back payments for child support. I never got this money and he never got it so my question is where is it?? I moved from Washington state to Kentucky and have yet been able to get into the child support office to switch over Kentucky. I am not sure if I'm in limbo or if I'm still registered with Washington child support since I asked for the paperwork to be transferred. Basically, if I am not "signed up" for child support, but they took the money from him for child support, how and when do I get it?