In the book that came with my freezer it says that food will stay frozen in an upright freezer for 24 hours and in a chest freezer for 4 days.
If anything has thawed to a significant degree don't re-freeze it unless you cook it or reheat it thoroughly first. That's a generalisation of course - not everything will cook or reheat successfully or might be dangerous to re-freeze - eg don't re-freeze thawed ice cream and I'd throw away any thawed rice to be on the safe side. Be careful, too, with any meat that has a disproportionately large surface area to the size of the individual piece, such as minced/ground meat, as deterioration affects the surface of the meat first.
(Incidentally, we've kept our chest freezers in a detached brick built garage for 40 years and had no problems with it and my cousins kept theirs in a wooden lean-to shed in the garden with no problems. It seems weird to me that if the temperature drops below a certain temp - 10C/50F? - the freezer will defrost but, then, I'm not a refrigeration engineer).