FYI, the proprietor of our B&B (Le Relais de la Tour Louise) was gracious enough to call the Hertz office in Bayeux for me a few days ago, and he confirmed with the staff that they are open 7 days a week, from 8 AM to 9 PM each day. It's not within walking distance from the rail station, but there are apparently taxis at the station that can take you to the rental office.
I finally found the station on Google Street View-it is right next to a Citroen dealership on Rue de Cherbourg (D613), about 400m past a traffic circle and ~3 km NW of the Bayeux rail station on route D613. Street View clearly shows a Hertz logo on the Total petrol station signpost in front of the station, and there are a few cars in what looks like a small lot to the right of the main station. Here is the link to the map I made for this route: