Have you tried to look underneath? maybe you could see it that way. If not I would think it will be easier to get a new pass than to tear the dash apart. Thanks for the post anyway, I'll try to remember not to put things such as credit cards etc up there.
Which side of the dash did it fall behind? If it fell behind the passenger side you could pull both glove boxes out then be able to get to all sorts of stuff behind them & the center stack (AC, stereo, etc.). If it fell behind the drivers side; best bet in that case is to drop the section of the dash below the steering wheel, the A-pillar cover & kick panel to give you more looking room. IF none if that works it might've gotten stuck in the foam padding (sound proofing) along the firewall.
Basically, your dash will look like this if you don't find your pass fairly easily.