First, before you leave: Fill a plastic cup about half full with water and freeze it. Second: Place a coin on top of the ice and replace the cup in the freezer. When you return, just check the cup. If the coin is still on top of the ice, all is well. If, on the other hand, the coin is in the bottom and the cup has ice in it, that means there has been a complete thaw and refreeze when the electricity returned. The contents of the freezer/refrigerator should be discarded.
If the coin is below the ice surface, but not on the bottom, this indicates a thaw that was not a total thaw. Again, to be safe, toss everything out.