NPC Spawn Issue: An odd mole in Kurns

[jballe3]

Hello. So, I've been waiting for an odd mole, trying to catch him spawning over the past few days (not consistently). I was finally able to catch him spawn at approximately 10:05 am EST on 22 June. I immediately engaged him. He was down to about 15-20% and he despawned. Is this supposed to happen? I know he's not up for a long time, but I don't think he should be despawning after he's been engaged.

Also, I do realize there have been other posts regarding this mob spawn. Some clarification would be appreciated.