Hmmm... I wonder what effect the pop had on the dry ice... Cause I used to do this as a kid...
I too was expecting to see fingers missing when the kid put the cap on.
I remember we also used to use 2L pop bottles, but we would crunch them down first to give ourselves warning. We would pour the dry ice chips in, then water and cap it.
When we saw the bottle start to expand rapidly we would be running and usually keep the explosion to our backs as I recall....
Thought about being stupid and trying with a glass bottle once... Thought again and didn't...Figure that decision saved me from scars...