Can't Find Song I have Previously Put on Playlist

[chloes15]

HI! I have the latest ios upgrade but even before that I have noticed that I have certain songs on my playlists that when they come on they get skipped immediately. Then when I look to find the song in my playlist by scrolling thru, it is not there. I went to try and find the song again using the Spotify search tool and I can see full albums but I cannot find the song (which I have already found when I originally created the playlist). Do you have any idea why this could be and how to fix it? 

Thank you!