My mare, has always wolfed down her grain as fast as she can, then go out get a drink of water, do a quick roll, and starts grazing.
One day, this was about two years ago, all those years of eating too fast, took a toll on her, and she choked pretty badly. They say horses colic because they can't throw up- yes well she choked with the impaction high up, so she was having stuff coming up out of both her mouth and nose. It's was honestly terrifying, and we were all kicking outselves, for what, we all weren't sure. Perhaps for letting her eat so fast all these years.
We finally got a hold of a vet (mind, this was happening at nine at night, on a Sunday), tubed and oiled her, and put her on antibiotics. She was fine by the next morning, and eating a small handfull with ease. We put her salt block in her dish to slow her eating, and we've never had the same problem again. She eats slower, since she has to work to get her food around the salt block. Plus, she's getting a healthier salt intake.
She's probably just really drained. It's rough on them. My mare also coliced mid-choke experience, just from fear and stress of it all. Is she drinking normally and everything? Just give her some more time to get her spark and strength back.
It's not your fault. It's one of those freak things. I would definitely soak it now though. We also added some oil to my mares feed to kind of lube it up, so help it slide down easier. Maybe try something like that as well? It's good for the coat if anything.