Do all pros have an official observer in the boat with them on Tourney days to ensure the catches are legal?

yes

http://www.bassmaster.com/news/2013-marshal-registration-opens-soon

I followed Boyd Duckett for a little while on day two of the Classic. He was all alone in his boat, but he had another boat following him with two people that he was talking to. We kept our distance, so I'm not sure what they were talking about, but I assumed that one of them was his marshal. I don't know why the marshal wasn't in his boat with him.

I would guess duckett had a camera man in his boat with his marshall following closely in another boat.

Marshals are in the boat with the anglers.  Camera boats are the extra boat.

I'm telling you guys, Duckett was all alone in that boat. No cameraman, no marshal, nobody was in the boat with him. My buddy took some pretty good pictures. I'll have him send me one, and I'll post it.

Maybe nature called.....