Austin's right, you have to add ice (I've used the re-freezable gel packs, but have since moved on to ziploc medium size containers filled with water and frozen (larger than bottles/melt slower)). About the shirt, every time I check on the beer, the shirt is sopping wet and cool (during the entire fermentation), so I figure it has to be pulling that water from somewhere, but like Austin said, might be the air!! Either way, I recommend the shirt, it certainly doesn't hurt or cost anything, and can only help keep the bottle cool and covered/not exposed to light (I use a dark shirt and dip it in the cool water when I start). And I forgot to mention, I put a blanket on top of the whole cooler to try and keep the cool air from escaping as much as possible!!
Duffman, you can see the frequency of my ice pack additions (gel packs) below, my optimal temp for that yeast was 68-73 (according to manufacturer):