Can you use open package of dry yeast that was not refrigerated?

Yes, you can use an open package of dry yeast that was not refrigerated, as long as it has been stored in a cool, dry place and is not past its expiration date. However, its potency may be diminished if it has been exposed to warm temperatures for an extended period. To check its viability, you can proof the yeast by dissolving it in warm water with a bit of sugar and seeing if it bubbles and foams within about 10 minutes. If it does, it should be effective for baking.