Did that in feeders all the time. Assign you an empty trailer to take out, planted a "seed" to see if you checked before you left.
Ironic in that if you do, meaning, a lot of times you had to climb up IN the trailer (not me) and walk it or pull over to ladder area, back up, pull up ladder, climb up and walk inside, climb out, put ladder back then pull to outbound and explain why you're late.
Side note:
Years ago, at an extended center, had to hook up set of empties to take back. Hooked and was checking for "seeds". In one was 4 SDA packages that were NOT "seeds". Of course took em in but wondered, because some of the MTs on the lot didn't move for days, how long they were in there.