Photos disappeared from iPhone after memory was full

Many operations use the iPhone's free space to move files around. If you run out of space, then those operations may not be able to be completed and, ironically, that can mean that even deleting doesn't work. If you have less than, say, 15 GB available, then things can get lost forever. I fear this is what has happened with your phone. The same thing applies to iCloud.

You can see this:

         If you're missing photos or videos in the Photos app - Apple Support

Basically the above says to look in Recently Deleted and in Hidden. Be sure to check your Library thoroughly-- the pictures may not be where you expect, as dates may have changed. You can use the search field with the date or location. And remember, you can sort the Library by date captured or by date added. Also, your Library view now has filters, and you may not have your filter set to "All Items.”

Unfortunately, if you don't keep your own backups to an external drive, then there really isn't any place else to look.

Yes-- so sorry…