I've done the same thing, except wayyyyy worse. We were leaving on a 9 hour trip and we got his DVD player all set up and everything in the car and my mom put him in. We leave and I look back at him no kidding, 20 minutes later and he is not buckled in. AH! It was crazy scary.
And you should totally get certified. I did a few months ago!
Where did you go to get certified, if you don't mind me asking?
As a funny update to this story... a couple days after it happened, dp picked ds up from daycare (where I work). DP texted me a couple minutes later saying that as they pulled out of the daycare ds told him "Thank you for remembering to buckle me up". LOL! Thanks for rubbing it in, kiddo