Instead of ice cubes in the freezer, I discovered a really big block of ice.
It seems at some point while I was gone, the power went out long enough to turn a full ice tray into a big block of partially melted refrozen ice. That would also explain why everything in the freezer was frozen together. When the freezer gets warm enough to turn half the ice tray into water, it's a good chance there was a lot of thawing going on with the other frozen stuff too. Naturally this makes all the contents of the fridge and freezer suspect, including the rib roast I was thinking about cooking up when I got back.
Well, I suppose I could look on this as an opportunity to clean out some of the dog hair that's made its way into the freezer.