iPhone 6s photos disappeared

My iPhone photo app shows that there are 0 pictures and videos on it, however the memory is still in use by the photos. They were there then gone. Not deleted. Is there any way I can find them again? I have tried doing a hard reset, attaching to PC and downloading, update ios (which the memory is full and won't complete even after deleting most of my apps) etc. Any recommendations? Thanks in advance!