I see this post has been updated for a long time, maybe the data loss problem is very troublesome all the time.
I think it is necessary to make a backup all the time, to prevent from data loss problem, and keep your data in a safe place.
If you don’t backup or sync the files of your phone, the only solution to get back lost photos is using Samsung photo recovery tool, I just use MobiKin doctor, it works well for me. But most of these tools is not free, cause they help you get back lost data in a simple way. If you want to get the important photos back to your phone, I think you need to pay one tool to solve this problem, photos are sometimes worth you to pay.
