Stylus just falls off?

A couple of years ago, I had a Van den Hul Grasshopper serviced and upgraded at the factory. A few days ago, I had it mounted by a well-respected local tech. I went to his shop today and listened to the cartridge. Then we disassembled the turntable for transport back to my home.

After the tonearm was removed from the turntable and placed on a shelf, I noticed that the stylus was missing from the cartridge. It is clear that no one and nothing touched the cartridge as it was moved. It seems that the stylus just fell out.

Has anyone experienced anything like this? (My understanding is that the stylus on these cartridges is easily removed and replaced, so perhaps it was not properly affixed to the cantilever.)