I rent an apartment in a two flat. A rabbit has made a nest in the backyard. The landlady has a lawn service that is due to come tomorrow, and the upstairs guy, who is not very nice, allows his child to run willy nilly around the yard. If I were to put a patio chair over the nest with a sign saying not to move it to try would the mother rabbit go back to the nest or would it freak her out?

She might be hesitant to approach the nest, but the urge to feed her young should be enough to get her to the nest. Be aware though that it will draw attention to the fact that something is there...both attention from people and other animals. If possible, it might be better to point out the nest to the lawncare service so that they can go around the nest.