"I'm thinking it was installed about 5 years ago. Why would that make a difference?
Most garage door openers installed in the last 8 years or so have a "rolling code"... meaning that the frequency of the signal that opens the door changes everytime you open the door. The old models had little dipswitches that you set and the frequency stayed the same until you manually changed it. The newer openers are much more difficult to "hack" into the frequencies.
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.