What excuse was given for searching the trunk in the first place? Nervousness? Confusion about his travel plans? Maybe Terrance fit a profile? Maybe somebody gave up on trying to get anything done through the Memphis *Crimestoppers* tip line, and called the right honest cop pal in Texas instead.
Once Terrance would have crossed into Arkansas on his way back to Tennessee, he'd have been home free.
. . . or maybe Terrance was just to stoned to realize what was going on. Don't Bogart that joint, m'friend, pass it over to me . . .