The puzzling part is their driving on past their home. Could have been they were arguing and didn't want to take it into the house: so they were driving on a bit while they talked or argued. Confusion ... two versions of who was driving. The person in the drivers seat is pretty conclusive, huh?
The mind loves a mystery. Ever notice that?
A well written mystery is the best kind of reading, but 2nd to Louis L'Amour westerns...
Your right the mind loves a mystery and also loves to fill in the details that are not known...