Now a days we have all these tv shows, crime shows and news stories, to learn from so a few ideas using the airport as an example of how to pull it off.
1 option How about packing a bag walking to another location, like maybe apartment building and calling a cab using wi fi & google voice number and paying cash for the ride to the airport, take the train back home.
2nd option packing a bag and getting a ride from a friend, or relative to the airport.
3rd option packing a bag getting a ride, taking a bus to the train station, or walking to the train station and taking the train getting off at the airport stop and walking 20 minutes to the spot.
Now if the person takes the train, paid cash for the ticket, yes there would most likely be video, but after 4 months would it still exist? Taking a taxi from a different address wouldn't show up right away, unless they checked with all the drivers to see if any passengers matched. Enlisting the help of friends or relatives would be difficult, there could be stories of you taking a trip some place. It could prove very hard to track if a google voice call was made to any taxi service, if you don't know the google account, and it was made over a public wifi spot.