Barn owls

Hi. I'm not sure how to post this. But I'm just wondering if anyone knows much about barn owls? We've been watching barn owls in a box for a while now, anyway tonight we went and the box was on the floor. Sad is an understatement. However we were last there on Saturday and it was fine then. But I told my brother he had to go and check because for all we knew they were still alive. There was 4 as far as we had seen, however, there was a dead one in the field last week which we don't know if it was one of them as we only seen one adult out. But anyway, my brother went into the field and lifted the box and one flew straight out, which was good because he flew and seemed to fly ok. But then a second one was a bit more confused but he did come out however, he looked to be too close to the water and kind of hopped to the fence away from the box. I did see him fly/jump up on the fence but I'm sure he was injured. We did try looking for him but couldn't find him. (I'm saying he/him but I'm not sure if they were male). My brother thinks they were both the young ones but they did have their main feathers. Now we've never seen the young out the box so we're not sure if they would know what they're doing. And I'm just really worried right now because I want them to make it. So is it possible the parent, (they've nested there many years), would come back to them or they would call for each other? I really don't like bad or sad news so I'm hoping someone can just tell me their instincts will kick in and they will be able to go on. It wasn't a huge fall to the ground but big enough to shock them. It was the wildlife trusts box but it was rotten my brother says. But it just seemed like nobody really cared much when my brother finally got through to them and they said they'd tell someone tomorrow morning from the wildlife trust. I know nature is nature and I know there's more chance they won't survive but is it possible they will be make it back from this? It's really sad to see this happen to them. I'm more than happy to take hate for telling my brother to go into the field as it was trespassing but the fact that we knew there was a chance they'd still be alive, would do it over and over again so they didn't have to suffocate or suffer knowing nobody was going to save them.  

Thank you in advance. 

Sarah