The film was loaded properly. It would not have stopped winding if improperly loaded.
I'll add one possibility not mentioned, although I think it is highly unlikely. It is possible that the camera is set up with the actual shutter release and the wind system release out of sync. It should be that pressing the shutter button releases both the wind system and the shutter itself at the same time. This is adjustable, and it isn't uncommon for the adjustment to be off, especially after service and the shutter and linkages being played with. It should be checked and adjusted as part of final assembly.
What this can lead to is that pressing the shutter button to a certain point will release the wind system, with a quiet click noise. And then continuing to press the button will release the shutter itself. If a user stops pressing the shutter button at the first click, there will be no exposure of the film while the film can be wound forward.
To test, you need to load the camera with either a test roll of film or the backing paper. If using backing paper, have the original lead end out- frame 1. You need the bit of tape holding the film in place to trip the Automat film sensor. Or put a piece of making tape on backing paper about 30cm-45cm from end to trip it. Now slowly press the shutter button and see if the shutter is released at the same time that the wind system is released. Do a few tests.
All in all it would be hard to not fire the shutter for a whole roll unless the adjustment is pretty far off. So highly unlikely, but it is a possibility. Maybe there is a decent offset of the two operations, and maybe your friend was paying attention to press the shutter button fully on the first shot, then relaxed and was pressing the shutter button gently after that.