400 Lost iPhone Pictures

I recently came back from France about a week ago. While I was there I took about 700 photos on my iPhone 5S. When I got home I downloaded the pictures to my computer and clicked on the button that said "erase after importing". It took a while to import but after it was done I checked the photos and I realized that it only downloaded about 300 of the pictures😟. I didn't back-them up because I was going to put them on the computer right away. I really want the pictures back and I have tried using recovery iPhone software but it does not show my deleted pictures. I don't know what to do😢. Any help is greatly appreciated.