I have removed the freezer floor and the evaporator cover (back panel) and could not find the drain hole. There isn't one in the drain pan, nor under the drain pan anywhere along the back bottom of the freezer.

I am assuming that you have the model with the freezer on top. That drain is on the bottom toward the back of the freezer. Pour hot water in it and look where it goes. The drain will be at the lowest point. Here are some manuals: https://dl.dropbox.com/u/8010163/Whirlpool%20Refrigerators.zip
You should be able to see it in one of the drawings.

Yes, the freezer is on top. I could not find a drain on the bottom toward the back of the freezer. I have poured hot water there, and it doesn't go anywhere. Thanks for the manuals, but they do not have my model, nor anything similar to it. I've looked online and seen similar models, which show a drain hole, but mine doesn't have it where theirs are. I need a drawing of my specific model.