My dad once had a yellow cassette tape of some synthesised music that I thought was great. He alleged that it had never been released, and we referred to it as "Voyage". The tape case had a label, with what looked like a track listing and catalogue number on it.
After years of looking, I finally heard one of the tracks being used as background music in a presentation, so I wrote to the people who put the presentation together to find out what it was. Unfortunately, they had no idea--the music was taken from one of those compilation a;bums that's made up for exactly this sort of thing, and was made several years before my enquiry.
Fast forward another few years. I hear another track from that album on a newly produced video. So I contacted its producers and met with the same answer: they got the music form some generic soundtrack record.
In the end, I decided to try searching for the (now very faded) what appeared to be track listing in google, and voila! The full details of the record from which the tracks came showed up. Another quick search later, and I not only found someone willing to sell me their vinyl copy but a new copy on CD too. I bought the record (of course!) and two copies of the latter, one of which I gave to my dad. By the time I finally got a copy, I'd been looking for nearly 20 years, most of which I didn't even know what I was looking for!
I still have that tape here somewhere, but of course it doesn't get played. I just keep it for sentimental reasons.
Oh, in case anyone is wondering, the LP is Voyage by Brian Bennett (ex drummer from The Shadows), and the two tracks used in the soundtracks were the title track and Ocean Glide.