I hope he feels better soon! don't beat yourself up over it, you're not selfish for not knowing.
Yeah, things like this happen, you can't know right away. At least him posting on FB shows he is probably alright.
Oh, that's awful!
Mugged?! That's crazy! Sometimes cellphones and Facebook and Twitter and stuff make us a little too connected. For better or for worse, we're a generation hooked on instant gratification. And seriously, don't beat yourself up about it.