Welcome to the site. I wish you were joining under better circumstances.
Okay, assuming that the fish seems to have this problem after jumping out of his tank, I would put it down to some kind of internal injury and not an illness. There is a possibility that it is something to do with the swim/air bladder. Fish that have problems swimming, or can't hold position often have swim bladder disorders. Normally it is caused by disease, but 4 feet is a very long way for a fish to fall and since they are used to very little gravity, so to speak, it could cause them serious problems when they hit the ground. If indeed this is the case, there's nothing you can do afraid. It may not be the swim bladder, the fish may have injured itself some other way. Finding out what injury it has is virtually impossible. Has the fish stopped feeding and is it breathing heavily at all. Also, have you checked the water conditions, ammonia, nitrite, nitrate and pH?
I would suggest that you monitor the fish for a few days. It may well improve in time. However, if the condition doesn't improve and the fish seems to be having problems, you may have to think about euthanising it. Anyway, let's look at this as a last resort and keep our fingers crossed for you