This is a long shot but in the circumstances, it's worth a try. Go to the Google Play Store and download Root File Manager. You don't have to root the phone to use it.
Install it and use it to try to find a folder named Lost.dir. It's Android's equivalent to Windows Recycle Bin and with luck, you may find your photos in there.
It's also worth connecting the phone to a Wiindows system by USB and looking around in there. You may discover something.