You are so right here Karen. Horses are reactive animals and stuff does happen, sometimes within our control (read dumb mistake) and sometimes outside our control.
One of the women I ride with put a bottle of carbonated water on her saddle. Guess what happened after she decided, at the end of a trotting exercise, to have a drink? Her solid good ol' boy appaloosa was totally fine about having a shower in carbonated water. Our daughter's Arab gelding, a wonderful older endurance horse with miles and miles of experience, had a none reaction when a goofy squirrel jumped from a tree and landed on his shoulder. I'd have forgiven either horse for having a "behavior" around one of these incidents. Nancy