Frozen solid? That's almost shocking. How cold is it where you live? Back on point, it depends really. Are the API test bottles sealed in transit? I don't remember if when I bought mine the individual bottles had little foil seals or not. If they are sealed, when they thaw out they should be fine. The chemicals are still the same whether they are a solid or liquid. If they are not sealed, I would be worried ice got into the bottle, thus mixing the chemical with water. That would throw off the accuracy of the kit.
Minnesota... it was only -13 today when it was delivered. Everything is fine and it's thawing quickly. Definitely sealed. I'll use it and judge based on how weird/off the charts the results are, I suppose.
Haha, don't worry I cleaning aquariums for a living, and I leave the test kits in my truck all the time. It doesn't effect the chemicals or the accuracy. Just make sure when you do use them they are room temp and you shake them up real well. I find that the cold separates the chemicals in each bottle more. They only thing that every gets affected by the cold is Live Bacteria products.