How to prevent upcasting n object C++

I have main class called Employee, where I have two subclasses PermanentEmployee and ContractedEmployee. I have to store both these types of objects in a same unordered_map<Employee>.

Then when I am trying to get them back from the map, both the types are automatically upcasted to the base type, Employee, and the attributes of subclass are gone !

Are there any method to stop automatically upcasting those objects ?

Or are there any method to retrieve those attributes back ?