Definitely me.The black belt caterpillar wrestler might hold the key when he / she says, "If you learn a song from someone else then you have a sort of mental recording of it".
I understand this premis, as opposed to writing a song, which in my case goes through a lot of changes before it's "complete". Even when you think its complete ,there is the odd bit of tinkering with the words as it develops.
I wonder if all the tinkering and changes brings on the forgetfulness.
It is embarrassing when the obvious deduction by the listener is - that you must be pissed - which is a little unfair at least sometimes !.
I know someone who (in theory) does not forget words to his own songs,when he does,he just gives an artistic grunt and groan , belts out the corresponding line from another verse and doesn't bat an eyelid at the end of a song.
Anyhow, who's giving out prizes for noticing someone sang the wrong words / line / verse , surely none of us ?.