Does it have an electric eye? One that stops it from closing if something breaks the beam?
If so, it is possible that an animal ran across as it was shutting and it went back up and was open all day for anyone to walk right into or someone was waiting near the door but out of site when your husband left for work.
The best thing to do is watch it close all the way before leaving your driveway.
It does have an electric eye. But my new neighbor was burglarized last month which makes me suspicious. He also came home to an open garage door. As you can guess I was out canvassing the neighborhood last night since the police seem to have very little interest in this matter. As it turns out, after he was burglarized, he had a monitoring system put on the outside of his house. He may have pictures of vehicles in the neighborhood yesterday that "didn't belong".