There is a term in the food industry called "active water". Active water determines the safety of a foodstuff to be left without temperature controls and still be safe to consume. Low active water foodstuffs prevent bacterial growth by making the environment within the food inhospitable to bacteria and even some molds. Bacteria need water to colonize and multiply. This is why you can leave a McDonald's french fries out and they will dehydrate but not grow bacteria or mold. Many foods are naturally low active water and are considered safe to consume without the need for refrigeration or added preservatives/microbe growth inhibitors. Most cookies do not require refrigeration nor do nuts and nut butters, honey, dried spices and many other low moisture foods. Even butter does not require refrigeration because of the high fat to water ratio. So...the food that comes out of the dishwasher stuck to dishes is very likely low active water and unlikely to colonize significant amounts of bacteria. It will continue to desiccate until absolutely nothing is going to attempt to eat it. I think stuck on dishwasher food is inert and therefore qualifies as a new form of food preservation, albeit a really shitty one. It won't kill you or make you sick to eat it, but I wouldn't want to.