tape that cup up. so that if the roots do form, no light can hit them- that would zap your clone. And you should try to find something to warm the soil, if the medium is warmer than the plant it encourages the roots to grow.
I went out and bought a hotbox for 28 dollars- its got a warming bad, a tray- pre moistined rockwol, and a tent to keep the humidity high...
Haven't used it yet, but it seemed like a great value, for the reassurance that less of my clones will die.