Well, the lab didn't make the frames overlap; but the camera didn't fog between the frames, either, so there is more than one issue here. I don't know how opening the back would not have also fogged the sprockets, or how it could have also fogged the film in the cannister, so it sure seems like something happened at the lab - while at the same time the camera did not advance properly.
Hey everyone, I finally got another test roll back from the lab, and everything looked great. Thanks for all your advice and sorry if it ended up being a slight waste of time. With so many issues happening at the same time it will remain a mystery as to what happened. Thanks again!