It sounds like it is very possible that he sustained an injury. When animals panic, they can often hurt themselves since they are not thinking clearly. It could be a neck, wing and leg injury he got. I would still give him sometime to see how he his doing tomorrow. Rest is the best way to heal an injury, as well as shock.
Here is a link for tube feeding. I wouldn't consider doing at this time, but these supplies are good to have on hand when you need them. They can sometimes be difficult to get, so I would recommend getting the supplies now.
https://www.backyardchickens.com/th...ng-guide-pictures-under-construction.1064392/
I would also measure out his food so you know how much he should be eating and compared to how much he is eating. Ducks should eat about 0.4lbs of food day.