What is the one CD you can't find?

Years ago I had listened to an audiophile test album with a white cover and little credits to go on the back side. I fell in love with it immediatly. The owner of the album was kind enough to make me a tape but would not part with it at any price. Later I discovered that members of the band Steps Ahead played on it, and even released one of the tunes on their cd. I have searched for years to find it on either cd or vynal yet have never come across it.This would be my greatest find. Just wondering how many others have a similar situation.And what is the one cd you just can't get?