If only one bracket comes off, movement stops only for the tooth it was on. All the other teeth that have brackets bonded and connected by the archwire keep moving. If the loose bracket isn't put back straight away, that tooth can quickly drift back towards its original position. It sounds worrying, but it isn't a big problem. Once we put the bracket back in place, the tooth moves back into line within a few days.
This answer is for general information. Your own case needs an examination by an orthodontist.