I recently got a Creality CR-10S, and for my test print I used the gcode on the SD card, but once I saved a file onto the removable drive and put the SD card back into the printer, it wouldnt register the SD card anymore. Any advice would be greatly appreciated.

Try another SD card or reformat the existing one. It is possible that you took out the card while it was still being written to by your computer and it made it unreadable.

Thanks! I went ahead and replaced the micro SD with a regular SD card and purchased a micro SD to SD card adapter off of amazon, and that worked perfectly.