Looking for suggestions to get my pictures back.

I recently upgraded my iPhone to the new 8. My 6plus was having issues and it was time. My previous phone was leased through sprint, so before upgrading I backed up my phone at the Apple store to make sure my pics would be saved. The back up was a little over 13GB. During the process my husband got called into work and we had to just set the phones up as new to get out the door. I erased the new phone and started my restoring my back up, but only about 20 of my 2900 pictures came through. The tech at the store told me she could see that how many pictures were associated with my account, but now I’m being told they aren’t in the back up and they are gone. I have a 14 month old and am missing about 5 months of pictures hat weren’t saved to my computer. Including his first birthday. Any way anybody out there has any other suggestions on what I may be able to try and get those pictures back? I’ve erased and restored this new phone about 14 times of not more.