Freefall 1309
Rescue!
How do you know..
The robots we're after know too much about this place to have just walked in. They knew the transponders were here.
They risked getting a bad transponder rather than open new boxes. They took one from the truck. Either they knew how the damaged box was inventoried or they have a strong inhibition against harming boxes in their care.
Funny how things always seem so obvious after someone else has figured them out.