Getting my pup spayed

I took my pup to a local clinic that did a heart worms test and a rabies shot for cheap and they gave me no paperwork on the shot, just a tag that says she has been vaccinated. To get her spayed the vet needs paperwork that shows she’s had her rabies shot. Now she was a stray so she’s never been to the vet as of right now and I’ve called the number on her tag to see if they could send me paperwork to prove she’s had the shot, but they never got back to me. Is there anything else I could do to get her paperwork or prove to the vet she’s got her shot, or will I have to wait until next year when she gets her next rabies shot and request paperwork?