IPhone 6S Plus froze on the home screen, I was able to screenshot, and then I manually shut it down but deleted a lot of photos when came on?

I have iOS 11, the home screen froze, I could only screenshot, so I did that, then I pressed the side buttons to shut the restart the phone, but when I turned it back on, 1,000 of my 25,000 photos on my Camera Roll were gone

How to resolve this?

**Also, I haven't backed up my phone in 27 weeks, since most of the 1,000 lost photos were from 2015, would the photos still be in the latest backup from 27 weeks ago (before this BS happened)?

Unfortunately I think they are irrecoverable, you should contact Apple about replacing your phone because only faulty devices would do something like that.