Strange drop in piety, equipment destroyed

[vesmo]

So I'm playing a lvl30 Dwarven Weaponsmith. I'm neutral alignment and sacrificed enough to Clamgaddin to get to the "-deity- favors you" level of piety (not crowned yet as I try for an ultra ending). I then proceeded to go to the frost giant caves where I have a greater vault with 10 greater red wyrms to do some looting. I heal in-between the fights by either regenerating off-level or drinking some potions, I think I used one or two prayers as well. And then, the crazy thing happens. I pray for health (last message was just the general glow in a silvery light, no ground rumbles or anything) and Clamgaddin TURNS MY EQUIPMENT TO DUST. I'm not doomed or cursed, so how is this possible? Similar thing happened earlier as well in the same cave when my deity cursed my inventory after what seemed like way too few prayers. Really puzzled here, anyone had something like this happen or is this a bug or what?

EDIT: It's been a while since I've checked up on the prayer mechanics and I guess it's just possible that I've prayed for health too many times, resulting in it being very expensive for piety. Guess this is the most likely explanation. Still really sucks that there's no warning from the previous stage if you don't drop low enough in piety to get at least the ground rumbles message.

[hapro]

I think they also get annoyed if you pray too many times within a certain number of turns, regardless of piety? I'm not sure though.

[zliplus]

When I was testing precrowning before, I could get dozens of empty prayers consecutively with no problems until piety dropped low enough. Also, 2 or 3 consecutive times early is perfectly doable (and necessary to get rid of poison).

Edit: in fact, I just had to pray for healing 4-5 turns in a row to survive when Roland the invisible black wizard summoned a bunch of ice vortexes almost next to me. Took ~40 damage each turn and I only had 45 max hp, so I didn't have time to even put on my ring of cold resist. On the bright side, the vortexes killed Roland for me and he dropped SLB! (But no kill credit means no achievement line)