Believe it or not, there are numerous groups that travel around the country with their sole purpose being looking for freight trucks to steal from if they get the chance.
Yep, it's a BIG problem for couriers. We used to get professionally organised gangs following our vans because we had a contract with a mobile phone company.
They used to follow the van and then run out and stand at the back door of the van whenever it stopped. If the driver came to the back, they would walk away and the driver would think they were just a pedestrian crossing the road, but if the driver opened the side (sliding) door, the central locking unlocked all the doors, so the thieves would pull open the back door a little. Then the driver would close the side door, activate the central locking and walk away to do the delivery.
The thieves then emptied as much as they could from the back and then fled. It happened about 2-3 times a year per van. In the end, we had private security teams following our vans, and even the local police. We had to get the vans rigged up with cameras and change the locking mechanisms.
It was disturbing how organised and well-informed the gangs were. They knew exactly which vans to target and when.
Then there were a few incidents where they simply stopped the driver on a quiet road, pulled a bat, knife or other weapon (thankfully never a gun) and then empty the van while the driver had to lie on the ground. A lot of it never made the news - bad publicity best swept under the carpet.