Bigfoot is found within the viewfinder in the Rocky Mountains location. You first need to place someone on the viewfinders looking out near the top of the screen. Then wait for them to ask for help finding something (crosshair over their head). Once you are in the zoomed view, ignore (and potentially avoid) the customer's object request. Move the viewfinder to the bottom left of the screen. His outline is visible by some trees near the shore. Hover the view over Bigfoot and the achievement will unlock. You need to reach 3 star rank to unlock this destination.