I think Cowan's must have gone under. However, I searched for this collection and found it listed on the Live Auctioneers website:
Larry Ness CollectionThis is a jaw-dropping assemblage of significant firearms from the western frontier. Several Hawkens (including a Hawken pistol), several Dimick rifles, California rifles, trade guns, firearms embellished and repaired in native style, several Remigton-Keene rifles as issued to the Indian Police...
Unfortunately, you need to register and make an account with Live Auctioneers to see anything more than the thumbnail images of the guns, but I just might do it. I can't see that it would obligate one to make a purchase.
Anyway, it's worth a look.
Crooked River Bob