Well, you certainly come up with some interesting scenarios. The funeral industry has actually come up with a name for the process: alkaline hydrolysis. Some universities have been using it as a way to dispose of the remains of cadavers donated to science. That process is a little more complicated because it also uses high pressure, as well as lye and heat. You can read more about its history and other details here:http://abcnews.go.com/Technology/story?id=4828249
I also found a video that shows how quickly a chicken's foot dissolved in plain, unheated lye. In just a few minutes, nothing was left but bone:http://www.youtube.com/watch?v=8IoH1rwYc68
Now for your scenario. After killing the guy in the drug deal gone bad, we'll assume the perpetrators have a huge vat they can heat to 300 degrees.They throw the body in. Within a few seconds, the skin turns a yellowish color. Within a minute, the skin, clothing and hair have dissolved. Because human ligaments, muscles, etc. are thicker and stronger than those in a chicken's foot, it will take longer to dissolve them, but within an hour and half, all we'd see floating in that vat is a skeleton. After another 90 minutes, nothing human would be identifiable. There would be a thick, oily tan liquid, and some powder resembling ash in the vat. This entire process would take 3 hours. As for anyone knowing what happened, investigators familiar with alkaline hydrolysis would know something thatw as once alive been dissolved in the vat, but they'd need a lot more evidence to gain any convictions. I must say, a pretty grisly, but effective, way to dispose of a body.