I did a bit of research today on memory and tips on how to remember lines in songs.
Its amazing how many singers can suffer from this and how many professional well know signers are effected by memory loss in a situation where they really need to not be making mistakes.
By reading further into this it looks like the number one reason is lack of connection to the song its self.
I also read that Ella Fitzgerald forgot the words to Mack the knife and that instead of looking like a fool she improvised the verse and it became a historic performance loved by many.
Formula to Remember words and learn songs.
1/ Write the words out while playing the track, break it down into Verses, Chorus bridge etc.
2/ Sing the lines as you type them.
3/ Break the song down into sections, don't try to learn all at once unless your superhuman. Learn each section first and paint pictures in your mind on what the lines mean to you.
4/ Hide the paper and listen to track again and see how much you can remember.
5/ Reapet the steps until you know it.