I also experienced an "accidental flush". I didn't know what the stones were then, but I recall having a copious evacuation, very soft, with what looked like irridescent green lumps. As with you, my accidental flush produced larger stones than the flush I did on purpose.
I don't recall exactly what I ate or did -- I think it was related to taking vitamin B complex, magnesium-multi mineral supplements and a couple tablespoons of fish oil after a day when I didn't really eat.
I'd drunk a bottle of wine (on an empty stomach) that evening and wanted to get some nutrients... My poor liver was probably in shock!
Frankly, I prefer the soft evacuation to the "butt pee" we get from Epsom Salts . But I'm not drinking now, which is definitely for the good.