Cell phone

If your photos are not stored on the internal memory of the phone then yes if somehow you lost the SD card you would loose the photos. Your best option is to download the photos to a computer and store them there for safe keeping. You cn check to see if the photos are on the internal memory by removing the SD card and see if the photos are still there.
 
Formating the SD card will erase what's on it and unless the photos are kept in another location then they will be deleted and if you don't load anything on the card you could recover them in an accidental format.