Quite often some physical sign on them. Some hair rubbed in an unusual place, or even some small grazes. I had one that used to get cast - I was lucky I could hear it from my bedroom window. But even if I hadn't heard, you could tell by the scrape marks down the side of the stable wall, and the state of the bed.
Does sound like something she could have done to herself though.....
usually marks up the walls/floor where they have been struggling and thrashing out, slipped shoes or shoes pulled off, sometimes horses injure themselves. But a lot of the time not much other than a horse stuck on the floor
!! Best thing i would do though if i thought a horse could/has got cast is to give it massive banks and see if they all have been pulled down the next day
I have a horse who has got cast 3 times in the last 4 weeks - ist time, I didn't know he had - but he had put his pelvis out and was lame (ish) and hadn't been out of his stable (snow).
2nd time was 2 wks later and I found him, pressed into the corner of the stable with his knee and his nose against the wall. the day after the chiropractor had been BTW
3rd time was a week after that, when I had given him huge banks (straw underneath to pack and solidify, shavings on top) - and he was lying out in the stable, with his hind legs stuck up on the bank....... can't win sometimes!!
Does sound like something your girl could've done squirming in the stable - my boy was tight over his sacro-iliac and took intermittent short strides on one hind leg - not lame as such, just not stepping though.
Tbh difficult to tell..fors and against..
1..bed messier than normal..1.something could have stressed him through the night?
2..kick marks on the wall..2.My boy isnt a wall kicker,but has a moment now and again
Cast can be like choke tbh..you may never know what has happened over night