Opportunity + preparation = great images. I hear you about being prepared for almost everything but you can't always do it. When Linda and I were on our way home from the Rottie National in Colorado, I had my camera with the 17-55 F2.8IS next to me and Linda had the 200 F2.8L in a case in her lap. When we stopped for photos, she'd come with me and I felt I had 90% of what I needed for scenics or wildlife. Oh, and I had the 1.4X Canon Teleconverter in my pocket (which I never used).

At shows, I travel with my gear in a Pelican 1510 case but when I'm by myself, everything is in a backpack so I can just strap it on and go. I've still missed some situations that would have been nice but mostly, those have happened when I didn't have any camera gear at all.

Sorry you missed momma and cubs but if you're prepared, you'll get them next time. The good news is, there almost always IS a next time .

Jim