Saruman vanishes under a rockslide? [3.2.0]

[Therem Harth]

So my Dwarf Priest is dueling Saruman. Saruman is down to about half his normal hitpoints when he summons a Vampire Lord. I don't want to be bothered with the vampire, and Saruman is in front of it; so I cast Earthquake in hopes of disrupting LoS. And...

Saruman of Many Colours wails out in pain!
Saruman of Many Colours is embedded in the rock!

No problem, I think, I'll just dig him out. But excavating the earthquake area reveals nothing. It looks like Saruman disappeared.

Is it normal for Earthquake to have this Word of Destruction-type effect, or is it a bug?

[Derakon]

If I recall correctly, here's how this works: monsters can't occupy the same space as rocks unless they have passwall, so when an earthquake lands a block on a tile with a monster, it tries to shunt the monster to an adjacent tile. If it can't do that, then the monster is deleted, Destruction-style.

This could easily happen if Saruman was in a confined location when the earthquake occurred. I once accidentally deleted Ancalagon with earthquakes when I was just trying to block him off from the rest of a vault (by using the earthquake to spawn new walls).