The only proof you can get is having a competent electrician check the campground wiring. I may be wrong, but I have never heard of a 45 amp circuit.
You may wish to look at this website
(clicky). It explains RV electric circuitry.
Stepping down a 50 amp circuit to a 15 amp circuit is common. I do it in my driveway to keep the refrigerator cold and the batteries charged. As long as you don't use appliances that total over 15 amps all is well. If you go over 15 amps the breaker should take care of the problem.