As an amateur retriever trainer and a hunt test judge, that is one of the more fundamental rules that are enforced. Heard many stories of hunting dogs out of sight of the handler getting the choke collar hung up on deadfall timber or a fence and basically choking the dogs to death.

Choke collars are a training aid and nothing more, and should not be used unless you are in direct control of the dog.

Glad everything worked out for you.