My iPhone 6 just deleted 2000 out of my 6000 pictures. How can I recover them?

So, yesterday, my phone started glitching a lot, which lead to me having to restart it five times. Once I restarted it the fifth time, I went to go look for something in my photos, and only 4000 out of 6000 were there. I've talked to Apple Support and they didn't know how to recover them, and so I've just been stressing a lot over my pictures, because they mean most to me. Has anyone else had this problem, and if so, how did you recover them?

Go on recently deleted on your photo part of the phone