Iphone just deleted random videos?

So I was deleting videos on my Iphone and I realized I was prompted to delete the same ones… Multiple times. I checked back and realized not only had the videos I had chosen to delete not been deleted but only the most recently taken (which were very important to me) got deleted, and the old useless videos are still there… Is there some process I'm not understanding about deleting videos that is not as straight-forward as simply deleting them? Also is there any way to recover them? They were not backed up on the cloud.

Because you have more than one album of pictures and videos.
so lets say I had the "cambera roll" album and added anther one lets name it "me" I take a picture of something random and its in the "me" album and in the cambera roll one to,

Make sense?