While a curator may or may not be aware of 100% of a photographers' output, what makes it into a show would be entirely dependent upon the curatorial theme and the images that fit that theme that are available to display at any one time. Very few museums would have sufficiently complete sets of any given artists' work that they could compile a show only from their own holdings; most exhibits are composed of pieces from the museum's collection plus works on loan from other museums and/or private collections. With more famous photographers, especially if the museum is designing the exhibit as a "halo" show to bring in a big audience, there are probably certain pieces that would be expected to be in the show, but with a well-formed curatorial statement, you can justify just about anything. I remember a big Ansel Adams show at the Corcoran Gallery here in DC a few years ago that had mostly his early works, and while it did have some well-known pieces (the flower on driftwood for example), there were as many if not more pieces that defy the common understanding of Adams' ouvre. They had a body of his documentary photos from the Navajo nation showing dancers performing, and they also showed some of his later advertising and commercial photos, as well as some of his color work. It wasn't just "Clearing Winter Storm", "Moonrise, Hernandez", "Aspens, Northern New Mexico" and "The Tetons and the Snake River". If they had those prints there, I can't recall. I do remember being quite taken by his early works.
Another show of Adams' work I saw over at the American Art Museum did show a lot of his "Greatest Hits" but part of the point of the show was to demonstrate how his printing technique and vision had changed over time - you could look at early and late prints of the same image and see how the early ones were brighter and less contrasty whereas the later ones were darker and punchier. Most museums would not have multiple copies of a single image, especially ones like Adams' signature works which are selling regularly in the multiple hundreds of thousands of dollars range, in their collections, and so they would have to borrow many of those prints from other sources. How a museum finds out who has what, especially if they have to go to private collectors, is not something I'm aware of though.