So OP, just so you know - not promptly treating a known illness or injury has a term. It's called ABUSE. Another term gets used as well, NEGLECT.
Cats are extremely good at hiding pain and discomfort. Behavior is not a good guide. By the time you see behavior changes, they're in agony.
To hell with your vacation. Take care of the cat, or you don't deserve to have a pet.
(yes, this is harsh. I mean every word, I'm not apologizing, and I'm not taking it back. Suck it up)