Wow, what a fright! I’ll bet that scared a few years off your life.
Sounds like he just got himself in a dip in the pasture and his legs were pointing up hill no matter which way he rolled and he wore himself out trying to get up. I’ll bet he won’t repeat the mistake of rolling in that particular dust hole for a while! Glad to hear he’s ok.
He was definitely in a gutter he couldn’t get out of. It’s right where their path is worn through, and then they’d dug it real soft so he just couldn’t get out of it.
Strong horse, done in by that!