- You can quote me
Guinea pigs have pouches far down in their throats where 'goopy' foods can accumulate. Chewed-up hay and vegetable matter clear through relatively quickly, although not immediately like humans do.
Critical Care is a little more like peanut butter, so to speak. It's goopy and has emulsifiers in it to help it go through a syringe. He will eventually swallow it all, but like peanut butter for a human, it can stick around a little.
Just keep doing what you're doing, and please keep us posted. Continued best to him and to you!
- And got the T-shirt
Guinea pig throats are tiny, and if there had been Critical Care in his throat, he couldn't have been eating anything else. The stuff was in his mouth, not his throat.
Are you feeding it to him by syringe, or is he eating it off the plate? If you're syringing it, you're probably not getting it far enough back in his mouth. It should be deposited at his molars so he can chew. Any farther to the front, and, as you've found, he'll just spit it out. It's hard for them to work soft stuff back to their molars because they've got a gap in their teeth.
He's doing so well, he even put on a little weight..
One of the concerns to to watch the remaining tooth to ensure it does not grow so long it contacts the roof of the mouth.
Overall, I agree with your vet.
It is tough when you don't have many alternatives (if you were in the states, I'd recommend Oxbow Critical Care as an amendment to add calories to your guinea pig's diet). Many pellets do have oats in them.