Okay. I have it. I'm listening to it now. I heard it years ago in a radio interview she did (and this is where my boot is from). On the show, she tells the interviewer that she did it with Billy during the RAL sessions, and they did it because she just loved the song. But because it wasn't written by her or by Billy, they didn't put it on the BTM album because it would have taken the place of one of their songs. "But," she says, "we WILL do it, it will be used. Maybe we'll do it live on stage..." I can't remember if they did it during that tour. I've sort of blocked that era from my mind.
And I seem to have the full song. It's a hard out at the end, but it sounds like it does finish. I can send it to you if you want.