I agree with TLB, six months ago it was warm when you installed the fan and the customer probably had a window or screen door open-a makeshift way to make up air. Oops, you are in FL. so forget what I just said, but I'll still bet on MUA. If you find something cool, like one of the ladies 128 cats stuck in the fan, please take pictures for show and tell!
I would go out and see what is going on with it. I charge top dollar and when a customer calls me back for whatever reason I at least make a trip out of courtesy. This is what separates us from the fly by nighters.
On the other hand once you get there if the fan is the way you left it..well then either upsell a better fan or tell her to pick out a fan herself and you can install it