A student in a NM class I taught a couple years ago had a similar story. He got struck in the eye and had to be hospitalized. When they scanned him to assess the extent of the damage, they discovered a brain tumor. If he hadn't been hit in the eye, they never would have had reason to discover the tumor until too late.
Awesome guy (and good shooter) who is alive and doing great today. I saw him at the SHOT Show earlier this year. Genuinely good dude...