What is the right action here?

Last Friday, I had my Insight in to the dealer for an oil change and state inspection. Today, I found the current registration on my desk. They passed the inspection and put on the new sticker without checking the new registration. They are not supposed to do that. They should have said "No registration, no inspection." So, I have all the things to make my car legal. BUT, they did not follow proper procedure, which could get them in trouble with the state. Should I let this go? Or call them and explain what happened? I'm not going to report them to the state, which someone who likes them less might do. Please discuss.