A SIM card (Subscriber Identity Module) only stores a small amount of data. This includes your mobile network provider information, phone number, and contacts in some cases. It is not large enough to store photos.
It sounds like they were assuming the phone had removable storage, like the microSD cards common for other phones. This is what you would typically remove and use a card reader for. iPhones do not come with SD card slots, so everything is saved on the internal storage and/or the cloud.