It probably helps that we're the only prius on the block, but still impressive!
To prove the theory, someone went to the owner's work at noon-time, and gave him a new shirt, collecting the one he'd been wearing for half a day. They took that worn shirt, and swirled it through the air back at the house; recharging the owner's scent in the air. The dog was asleep and away from the front door, and surprised when its owner arrived home at the normal time.
Maybe a sealed box that opens to vent the scent. You'd need to have the same box do the same, with no scent too.
They also take her to a local pub that is dog friendly and she has friends there. She knows when she is going there as she starts getting excited when the car turns right at a certain roundabout. Go left or straight on, nothing, but turn right and she's right up all excited!