How to tell if a bunny is spayed

I have a neutered male rabbit ive been thinking about getting a partner for. I'm only going to get a spayed female, but its hard to tell if a female is spayed without papers and the owner of a rabbit im looking at says she doesn't have them due to moving all the time and often having things in boxes or tossing out what seems to be trash. I'm going to go see the rabbit tomorrow, so does any one have tips on how to know if a rabbit may be spayed without papers? I know they sometimes don't like to use litterboxes/and or mark if they aren't spayed, so should I ask her if the rabbit has frequent accidents using the bathroom? I just don't want to purchase a unsprayed rabbit and have her attack my other rabbit if they are ever out together. *I should add I brought my rabbit to the female I've been thinking about getting and they spent about 15 minutes together and seemed to get along so maybe they could be bonded in the future*

There is absolutely know way of knowing for sure without cutting her open and checking! You’ll just have to believe what you are told, I’d imagine.

Sometimes you can see/feel a spay scar.
However rabbits have such thick belly fur that may be hard to find with out shaving the belly again...
Not all animals wil have a scar though either.
Might be worth feeling around her belly skin for one atleast. You never know.