It's horrible having to leave him with the vet, especially when you're not expecting it, so sending you some hugs
But on the positive side, the horrible grass seed is being sorted out and it shouldn't be long before you have your boy back home, probably a bit woozy and sorry for himself, but free from the pain of the grass seed and with some eye drops to soothe and heal his eye.
My William had an unexpected sedation a few months ago. I took him to the opthalmic vet because he had a tiny lump under a top eyelid and she decided to keep him in and remove it under sedation there and then
. When I got him home he was sleepy and a bit wobbly (I lifted him out of the car in case his legs gave way jumping out) but after a couple of hours of feeling sorry for himself he was back to normal and ready for his supper.