It's also so so common to ignore pain in the heat of the moment or not really feel it even when you later turn out to be seriously injured. When I think of painful injuries I've had - a broken wrist as a teenager, a toenail torn off in aikido, partially torn tendons - at least 50% of the time I kept going and only noticed I was injured after the adrenaline wore off.
Same here. When I've been running whitewater in a situation where an interruption could be fatal, I've taken some shots where I knew I'd been hit, but it was almost like reading the word "PAIN" on a piece of paper rather than experiencing it: a "PAIN" signal that didn't involve any feeling of pain. The only time I've ever felt pain in such a situation was when it was a pretty serious injury, and even then it was muffled.