brake controller short

I went to my storage lot to get my TT for our Thanksgiving trip. Hooked up the truck and tried to pull out of the lot and the trailer wouldn't budge. After I investigated, I noticed the brake plug was pulled out of the trailer and was dangling by the cable. I was scratching my head on how this could happen since the trailer hadn't moved and ther was plenty of slack on the cable. I wrote it off as someone messing around. Put the plug in and was able to pull the trailer out of the lot. However, I noticed that my brake controller screen was red and was saying I had a short. The brakes seem to work fine (both manually using the lever and when pressing the brakes on the truck). Besides trying to figure out how the plug got pulled out, I need to figure out what's going on with the brake controller. I am leaving for home tomorrow. Anyone have any ideas in what to look for?