Ogg Vorbis file not listed in media player
Ah, this is because it is listed as an Unknown piece by an Unknown artist as the only piece in my library. The Ubuntu Rhythmbox program I used to make the ogg vorbis file did not tag automatically for this particular piece, while it did for others. 

The solution is to tag the file with for instance the "Audio Tag Tool", then it is searchable in the Android Music Player.

Understandable, but not obvious to me, I think it would make sense if the player app would search by file names as a last resort if no other matches were found.