I'm more curious as to how people actually tell the difference in restaurants/wherever. You could easily say "Oh I stole this from a glacier" when in reality it's just regular ice.
He most likely would have sold it to a specific resturaunt that was interested in such shady dealings (underground pubs and such). One can imagine that Glacial ice is probably more special than regular ice in that it's less likely to melt as fast and blend with the cocktail.