Sounds like the boggy area was in/near their pasture. We had a close call a few weeks ago with a low area in one of our pastures. It’s been ridiculously rainy this spring in the northeast, and we didn’t realize the mud in that area had gotten so deep. One of our older horses got in and had a very difficult time getting out. Thankfully, with the help of barn staff and some encouragement from a bucket of grain he managed to work himself free without need of calling the fire department. Needless to say, that pasture was closed until we could fence off that area.