I have a concrete floor as the model room is in the basement. The floor is painted a light gray color that has a little bit of a blue tint. I vacuum the floor regularly and keep it clean and, as a result, can usually find a runaway part easily. One other thing that I do: I wear a long shop apron at the bench and, when dealing with small items, will attach the two lower corners of the shop apron to the framework under the bench with metal spring clamps like those used for holding sheet paper together. The apron will catch the part before it hits the floor and saves me from having to get down on my knees.
Joe