I have never experience this, but I have rented lots of vehicles. Often your typical rental agency, Hertz, Avis, etc, don't want you to tow with their rental vehicle, or take it off road. I've even had to sign a wavier about not taking a rental off road. On top of that, unless your trailer is minimal, then a typical rental truck might not be properly equipped. On top of that, when you get in an accident, unless you have some kind of special insurance, the company will only rent you a car that is like $20 per day, so compact if your lucky.
I think you would have to wait, or find a specialty rental agency at your cost.
I could be wrong as it has not happened to me, but I would be surprised if a rental agency even had a vehicle that could tow anything but the smallest trailer.
