This is a sad example of a dancer who got lazy. Unfortunately, it happens way too often in this industry. While contracts can protect your work between choreographer and client, when you teach class, you unfortunately put your work out in the open for others to steal. Using it in classrooms is one thing. Using it in competition is quite another! You have made great strides in making sure your work is protected. Taking videos of your choreography is a sure-fire way to prove that your work came first. Also, in letting the organization know about the infraction, you have not only cleared your name, you've warned others about the character of the one who plagiarized. Obviously, if someone asks for a reference of this guy, you will not be passing on his information!