Well Steve how do we know the truck wasn't reported stolen ? I don't think Columbo would have found out as soon as he did if the gardener hadn't told him when he was being questioned.
The gardener has lot's to do working on those very large yards, plus how do we know when he noticed his truck missing ? We really don't know that either.
-hbe

Maybe this episode takes place in the "24" universe, where any two points in Los Angeles are no more than 15 minutes apart (unless the character needs to be delayed till the next episode...)