Since the refrigerated drugs would probably only be a partial load, they would be loaded into the nose (front) of the trailer, then an insulated barrier placed across the trailer and the unrefrigerated freight loaded. There may be a side door for access to the nose of the trailer. Refrigerated freight is packed as tightly as possible, and because all that weight is in the nose, can result in the axles of the tractor being technically overloaded, even though the overall weight of the trailer is legal.
Frozen freight is fairly easy to see if there has been a thaw/refreeze cycle. Refrigerated freight can be harder to tell. For high value refrigerated freight, most modern companies have a broadcaster that reports the condition of the thermo-unit and the temperature of the freight. When you have several hundred thousand dollars worth of freight in a railcar or truck trailer, this is cheap technology.
Transport times are usually well known for regular shipments such as this one would be. The person unloading should check the load date versus when it arrives. A big difference would be investigated further. Immediately checked would be the status of the thermo-unit. Just like with your car, you can plug in a device that tells what the unit has been doing.
I would see this as more likely to involve the driver who shuts off the unit a mile or so down the road, then turns it on later, but runs a normal trip time. Depending upon the length of the trip, and the time value of its transport, you could have either one or two drivers (two drivers can run nearly a full 24 hours in one day).
It's been many years since I dealt with refrigerated freight, but there was discussion of strips to indicate whether the freight had dipped above or below the temperature range. I'm assuming that would now be available, but I don't know.
And the more temperature sensitive the drugs are, the more controls you're going to put on it. Fruits and vegetables have been shipped from California to New York for over a century now, and meat a little less. It has been thrown onto railcars and trucks. It has minimal supervision during the trip. And a bad load of strawberries is a six figure loss. With food products you can tell. My guess is refrigerated drugs would have some sort of quality control check.
By the way, the shipping company wants to be able to prove that the trailer or railcar worked. It is not unknown for a warehouse in California to ship a bad load of fruits and vegetables, seal the trailer or railcar, then try to blame the shipping company. Since no one checks the inside of these units, it's very easy to do.
I think you'd have to fake the temperature record on the trailer to make this work.
Best of luck,
Jim Clark-Dawe