I sometimes have to work my memory without the piano.
I listen a record of the piece, while reading the score, and I play only the left (or right) hand on a table. Then I try to play it without looking at the score. Then I don't listen at the music, I play only with my mind. I do this from time to time, with one hand or two, in short sessions (minutes), because I get tired. It works for me. Sometimes this technique does not work immediately, maybe the next day, or in two days.