Q: photo lost iphoto library

Howdy Lighthousekenn,

It sounds as though at some point your iPhoto library has become corrupted, producing the result that iPhoto will not launch. I would suggest that you rebuild your iPhoto library using the steps in this article -

iPhoto 6 and later: Rebuilding the iPhoto library - Apple Support

Once this has been done and iPhoto is able to launch normally, try to launch Photos. If this has issues, follow the same procedure (holding down command and option when launching Photos) and attempt to repair. 

This help page has information about repairing the Photos library -

Repair your library - Photos Help

Thanks for using Apple Support Communities.

Best,

Brett L