Unless a symbol is assigned a unique package - such as by creating a symbol called <unique_device_name> and then creating and assigning to that symbol a package also called <unique_device_name> - there is no way to map a package back to a symbol because in many cases several symbols may use the same package (i.e. how many devices use a SOT-23 package?). This is not always true but in this instance all the schematic symbols and PCB packages named `cherry mx switch` appear to be listed under `User Contributions` and there are many symbols that are assigned the same package. The only way you can do this is go through each schematic symbol that is assigned a footprint that has exactly the same name as the one you chose to use and carefully inspecting each symbol to ensure it is correct for your application (open each for for editing to be sure: you do not have to save it). For more about this please see: https://easyeda.com/forum/topic/Create_Schematic_from_PCB_design-GSM4mfxP7 and: https://easyeda.com/andyfierman/Welcome_to_EasyEDA-31e1288f882e49e582699b8eb7fe9b1f