The next day, the ant's nest was gone.
In hindsight, it was almost certainly the mushrooms. Thank goodness we didn't have the kind of kids who would have dared each other to drink some... that could have gone legitimately badly.
Decades later, I mentioned this to my father and he recalled that there was this ants nest that he had intended to take care of, which he remembered for that long to give a sense of how out-of-the-ordinary this was. He was surprised when it just disappeared entirely one day, and perhaps just as surprised to find out decades later why it just disappeared.
Nobody needs to report me... I'll turn myself in.
I have to admit I posted this just so I could use the word(?) "formicacide". It seems an opportunity unlikely to arise again anytime soon.