That's not quite true. They can get samples but would have to send probes up his vent and down his throat to get them, which is expensive and stressful on the snake.
If anything else is expelled - from either end - save it in a plastic baggie with a little distilled water to keep it from drying out. Your vet will want to test for parasites and cryptosporidium.
I wouldn't feed him anything for at least a month, just keep his humidity up so he doesn't dehydrate.
Bear in mind that since you had him close to your other snakes, if this one tests positive for parasites the others will likely have picked it up also, so they should all be tested and treated accordingly. Until you know what you're dealing with nothing should come into or leave your collection.