I met Robin Zander like that at Toad's Place. He was having a drink and a cigarette at the bar before the show (glasses and the cowboy hat he often wears). It's a small place, but I don't know why no one else noticed him. I just sat down next to him with my friend, and we both minded our own bidniz. As he finished his drink/cig and started to go, I turned and said "Knock em out, Robin. You're the man" or some horseshit like that, and he smiled, and put his hand on my shoulder and went off to work. Very casual.
As for Marillion, another Toad's story (and relevant to the "doing other things..."). I had just watched the Seasons... tour show (H killed it), was hanging for a few beers (Toad's is a bar as well as club), and when the line died down a little, I went to the down stairs bathroom to pee. I hung the fire hose and notice Mark Kelly to my left, and Ian Mosley to my right, doing the same thing, just staring straight ahead. I felt it appropriate to not say a word and CERTAINLY not offer to shake hands. They zipped up, turned and left, and while I didn't talk to them, I do have a decent story.