Even though I couldn't find evidence to support my assumptions, through my own observations in the kitchen I'm pretty sure microwaved foods cool faster than foods taken off the stove and out of the oven (at least it appeared to be so).
I did find evidence that microwaved foods are often heated unevenly and that there can be "cold" pockets throughout the food due to its composition and shape. This can contribute to the food cooling off more rapidly once it is removed from the microwave.
I have referenced a website that may shed more insight on the subject.
In microwave heating , heat is generated by molecular friction between bipolar molecules (water). Because water is easily stimulated, heat is very suitable for microwave cooking. Microwaves penetrate the food and warming them from inside to outside.
Another major problem in microwave cooking is possible survival of pathogens.
Disadvantages of microwave heating are the inability to crisp foods, cooking unevenly and excessive drying of foods such as bread.
Understanding the process of cooking in the microwave and the changes occurring in food properties, during cooking, are significant in finding solutions and providing heating instructions for food protection.
Microwave ovens heat food quickly and efficiently. This makes them unsuitable for cooking certain foods, or to achieve certain effects. Additional kinds of heat sources can be added to microwave packaging, or into combination microwave ovens, to add these additional effects.
Microwaving food may raise safety issues, but it does reduce certain risks, such as that of fire from high temperature heat sources. In reality, microwaves are absorbed in the outer layers of food in a manner somewhat similar to heat from other methods. The misconception arises because microwaves penetrate dry non-conductive substances at the surfaces of many common foods, and thus often induce initial heat more deeply than other methods. Depending on water content, the depth of initial heat deposition may be several centimetres or more with microwave ovens, in contrast to convection heating, which deposit heat thinly at the food surface.
Yes, using the microwave isn't the perfect method of heating up food. It gets cold in minutes, unlike using the oven or the stove top, where food stays hot for a lot longer time.