When the blue Sofa is being removed from the apartment towards the end of the film, it is obvious when outside the building that the cushions the money is meant to be hidden under are removed to make it lighter to carry.
In the beginning, when Ellen first has sex with Daniel, she is lying on top of him and adjusts her position, at the moment the phone starts ringing. If you look carefully, you can see the flesh-colored tape covering the nipple of one of her breasts.
In three years, Ellen never cleaned the sofa or moved the cushions, to find the money.