I am towing my 2005 Prius on a dolly. When loaded, he beeped at me in that plaintive way that means "I'm not happy and I'm going to drain my starter battery!" Usually I just turn him off and on again, and that makes him happy. I couldn't make him happy, so I decided I'd live with it if he needed a jump later. Opened him a day later...still on the dolly, and he flashed the internal hazard lights at me and beeped a great deal more. Clearly he's trying to tell me something, but I don't speak beeps and lights. Anyone more conversant??
Flashing lights and a beep is generally the door lock/unlock situation. Was the Prius every in READY mode? Do you have the SKS key nearby or in the vehicle?