One of the most amazing trips of my life was to the original dig site in Dinosaur Provincial Park, Alberta. One of the early digs is left in situ as an exhibit. The dinosaur skeleton is laying in the ground, almost perfect, but it is missing its head. It really gives you a sense of what it was like for these early paleontologists, and what a guessing game it was at times to reconstruct what they were finding.
AS NC says, science is amazing that way. The puzzle of finding little bits and pieces and testing them to see where they fit. Sometimes a piece seems perfect, yet along the way something else comes along and you realize the fit was incorrect. Science is a constant readjusting process, which is why even things we accept as truth are still called theory.