Technically there is a slight amount of rubber spring back for a fraction of a millimeter and the air traveling with the rotor surface puts a small amount of pressure back on the pad and pushes it imperceptibly backwards. Of course that is only really effective if your rotors are perfectly flat and warp free, which most peoples are not because rotors never get resurfaced any more and 95% of them are super cheaply casted and turned which leads to warpage extremely quickly.
