Sounds like it could be an oversight issue. Once the party decided to bail his job was to bug out, not die by sticking around. It probably also mattered how much damage he had taken so far, if he only had 1d4 hp left then sticking around to become a corpse for his friends to deal with wouldn't be prudent. On the other hand if he had enough juice to live one more round some kind of distracting action should have been made to help the caster & archer get clear. If this was after hours of sitting around a table sometimes a reminder is needed, can't expect your players to be in top shape after long periods at the table.
-What you might want to do is create a top 20 list of things he should aspire to do as a paladin so it's clear to him and you. Remember, a paladin is not a catholic priest, paladins actually live in a world inhabited by demons, there is no turning of cheeks to a goblinoid. Good, not dumb. say it with me, Good, not Dumb. Finally, it's his Paladin. Everytime I play a paladin people want to tell me how they would play theirs and how I should live up to that. It's his character let him play it. If you have expectations of good let him know what those are & let him justify his choices. If their crap strip him of his powers after his next non-paladin act. Make it quick & clean.
A true story: Last fall I found a wallet in a parking lot, there were $20 dollar bills laying all over the lot. I ran around picking them up ($176 I still remember). There was close to a grand in the wallet, mostly hundreds. I was in a rural area, figured it was someone's whole check, rent money. I looked the guy up, called his employers anyone I could find, spent hours on this. Finally got a hold of him and he said thanks and drove away in his BMW with all his money. I was not happy with that response.
If you expect his paladin to do good deeds like that without a second thought then you need to remind him of the intangibles, the non-cash benefits of doing the right thing. Otherwise you should recognize that while RL priests can be lawful good people, they do charge for presiding over weddings. Good shouldn't mean flat broke all the time.
