Which phone model do you have? It's possible to retrieve deleted photos and other files by using a data recovery software. I personally use EaseUS Data Recovery Wizard. It works and I recovered all my files when my hard drive crashed. You can also use it with your phone (PC connection using data cable required) and memory card.
You can download the EaseUS Data Recovery Wizard here. There are a lot of other data recovery softwares available. Just use Google to find them. Good luck!