similar thing happened to me, senegal bichir jumped out of the tank and into the overflow, which wasn't in use. fell down through the hole and wandered around on the floor overnight. when i found him in the morning he was hard, dry, covered in dust and dirt, and not moving. got a paper towel (burial shroud to wrap him up in) and he twitched. i couldn't believe it. put him back in the tank, moved him back and forth in the flow of the filter, and after only a few minutes, he "woke up". once all the dirt was gone, the only damage was frayed fins and a slight scrape on his side, which has healed completely without scarring.