That's good that he passed whatever was in, and I'm glad that you're educated about crypto now!
Thing is with the testing you can't test 3 times in a day, it has to be done over several months or weeks.
If your snake passed a big poo and some gas then it's likely not crypto, and like I said I'm really glad your vet is competent enough to know what it is.
Even with your snake passing poop though, I would be wondering what caused the poop to back up in the first place. Was there anything strange in the snakes poop?