Alas I have a question, did the photos save to the internal memory? You have ti change the settings in the camera mode to save to sd card.
Secondly, did you format the card in your settings for the sd card? It has to be formatted to your device to really work well.
Third there is a app called Astro File Viewer Browser from the Google Play Store that you can view the sd card files, photos, documents etc. With ease. It also lets you view and transfer from internal memory to the sd card. You can also search for the photos within each internal and external storage.
The photos may be in internal memory.
The Galaxy S4 has a pre-installed app called "My Files" that will allow the OP to check both the internal and external memory of the device to verify the files are there and basic copy/paste functions.
Ah ha...! Thanks for telling me.
I use Astro its a good app and free.
I also use another third party file explorer (Estrongs/ES File Explorer) for more robust functions, but the "My Files" app works for a quick look and users who may not be as familiar with the android system.