The message here maybe should be to keep current on your annual physicals and pay attention to small "messages" your body is trying to give you. Youth does not automatically guarentee freedom from medical conditions.
I wonder if it might have been related to overexertion, which can certainly trigger problems that otherwise may have never been realized.
I think that pop culture advertisements like "Just Do It" and "No Fear" encourage people to ignore those little messages your body tries to send you. They imply that if you do ignore them, and you just keep pushing yourself harder, you can do amazing things. That 20-30 age group has grown up with that BS.
Ten miles on Ozark and Ouchita Mountain trails is a tough day for even seasoned hikers. I've never even attempted it. Maybe that's because I come from the "Take it Easy" age group.