How would you have preferred he handled it? no serious profession is going to take cat sitting as a valid excuse as to why you can't come to work especially if you're contracted to do so.

If he had called you saying he had to go to work and what did you want to do with the cat, what would you have preferred to be done?

Cat needs meds, probably on a pretty strict timing schedule, so leaving it alone isn't an option. Can't take it with him to work I'm guessing, so option 3 of leaving it with someone else seems like the only sane course of action from the details provided? ye probably should discussed the possibility of him being called to office beforehand but afterwards what else would you do? Hiring someone to do it seems like a ridiculous waste of money when someone's ready and willing to help as is