Yes , these were severe circumstances tho.
Many years ago my complex flooded -flash flood- and those of us on first floor left in water above our knees...in a hurry. Some hours passed before we could return, neighbor forgot about a revolver. Took awhile for gunsmith to soak, but I don't believe any parts had to be replaced, just remove rust, polish up, re blue.
Fire...this is a bad dealie. I had customers over the years that suffered fire damage, the water and chemicals wreaked havoc on everything as you can imagine. Those that actually became "heated" were a loss. Most of the water / chemical damaged were able to be restored.
One fellow was caught on a lake during a storm. He kept his nice dress watch and gun from rusting by tossing in a big zip-lock bag full of water, and into the livewell until he finally made it to safety.
No oxygen meant no rust...just required both being taken apart "clean ,oil and adjust".