I'd have to ask whether the rider was using earbuds or headphones. Fixie?

I've jammed my crankset on occasion with a bad shift or chain suck, or something, and haven't sent myself flying. So jamming the chain and cranks causing the bike to stop would almost require a fixie. Of course, there are also problems with getting stuff into the spokes.

The next issue is why the rider got hit in the face with the handlebars. Ape Hangers? One possibility is that when the cell phone (or walkman) got lodged into the chain, the headphone system failed to come disengaged, yanking the head downward. And, thus my question of earbuds vs headphones. Wrap-around headphones may have had more of a tendency to pull the head downward, whereas earbuds might simply pop out (with a little downward pull).

Also, note those people who like keys and ID cards on a dangly necklace should have breakaway straps, especially around equipment.

I do listen to a radio if driving alone in a car, but not when riding a bike. I feel that it would detract from my ability to pay attention to the surroundings, but that is a completely separate issue. I do a lot of riding on roads, some with a high speed differential. Mostly MUP riding might be different, although one is never truly isolated.