Almost ran into this issue on the wifes car recently. She has a 2005 Malibu and the brakes weren't working as well as they should have. Went to Napa, bought some new pads for all around (thankfully they had a 20% off bucket sale which saved me like $30), went home, and got to work. Got the fronts on no problem then turned to the back. That's where I ran into that mysterious tool posted above. Having had a few cold but refreshing beverages and being after 6:00pm, our Napa was closed. Did a little google-fu and found a shade tree trick that I'm sure some won't approve of. Was able to take a big ol' pair of channel locks and CAREFULLY retract the caliper cylinder back in. Started the car and tested the caliper a few times before I reassembled to make sure it worked like it should and I was good to go. Cars been driving (well, stopping) great for a few weeks now so I'm pretty sure I'll be ok but time will tell.
Anywho, sorry to hear about your trouble. If we were closed, I'd be more than happy to lend a hand helping you out!
