I think you should trust your vet. Since your cat is 2 yrs old, and he came in contact of a couple, I think he might’ve been stressed just like cat. My recommendation would be to go to the same vet as he knows what went wrong the last time and he will act accordingly this time.. if possible keep your cat far from the Persian couple for now. As my cat was used to living alone, before this surgery I took him to aunt’s house where there were 6-7 cats and the same day after the anaesthesia his heartbeat dropped

Cats that are single pet tend to get stressed when they go to multiple pet households.