Sadly this story has brought tears to my eyes and I know just the pain you are going through.  May 5th 2007 my beloved pekeapoo girl Minnie, who in the entire almost 10 years of having her, she never ever ever left our yard.  We could let her out to pee and she'd come right back inside, of course with one of us being out there, we'd still go out to just keep an eye.  I was at work and my step dad came to let her go outside to go to the bathroom and in the split 2 minutes she was out there it started to thunder ( she was terrified of thunder and fireworks) she lost her mind and ran out of the yard and down onto the road and was hit, they never so much as stopped or anything. Infact nobody did.  That was so hard for me because it was so unexpected.  So i know how that greiving process goes and infact its been a year and I still cry cause I miss her like crazy.  She was such a wonderful dog and didn't deserve to go that way as I am sure with Typhoon, he didn't deserve that, no furbaby does.  So i am so sorry for your loss, it hurts in the worst way!