How did WH get to work after dropping off the truck?
If that's actually what happened, then he had to have someone following him to pick him up & give him a ride to work after he put the truck key in the mailbox.
Or, that's actually not what happened at all. (Sorry Zach, but I'm being super-careful here). He had to come up with a story to explain why the truck was there that day in case someone saw it. Neighbors seeing the truck and car later that afternoon didn't actually see AJ but just assumed it was her driving. The truck is parked back in the drive and the white car leaves just before (interesting timing there) sister is due to arrive home from school.