Yeast requires specific conditions to thrive and cause dough to rise. When yeast is mixed with dry flour and left overnight without additional ingredients, such as water or sugar, it is unlikely to rise significantly. Yeast needs moisture and a food source (usually sugar) to activate and produce carbon dioxide gas, which causes the dough to rise.
If you intend to make bread or any dough that requires yeast, it's best to follow a proper recipe that includes the necessary ingredients and steps for yeast activation. Typically, yeast is activated by mixing it with warm water (around 110°F/43°C) and a small amount of sugar. This mixture is left for a few minutes until it becomes frothy, indicating that the yeast is active and ready to be used in the dough.
If you accidentally left dry yeast in your flour overnight, it is unlikely to have the desired rising effect. It's recommended to start with fresh yeast and follow a proper recipe to achieve the desired results.