I don't think it's respawning at the spot where it was destroyed. I think it's respawning at the spot where the rest of the fleet is at the time it would normally depop. Rather than despawning, all the ships just come back. I observed this after getting into a PT boat and chasing after an enemy fleet a little while ago. Our CV had been killed. A minute or so later I turned around and our CV and cruiser were back, right there with the destroyers that had been left.