Yes you are missing something. I had the same issue finding mine, until I got in there with a flashlight, a rag and a pair of needle nose pliers.
The fitting you are looking is not a zerk. It's a little silver fitting with a ball in the center, located inside the u joint knuckle nearest the transfer case. Rotate the shaft until you can access the inside of the u joint and using the needle nose, use the rag to clean out any gunk in there. If that doesn't expose it, rotate the shaft 180 degrees. That little bugger is in there.
2012 Dodge C3500 DRW 4x4
2012 Keystone Montana 3100RL