These hidden gems are "hidden" in a variety of ways. It could be a piece from somebody unknown or even an amateur. It could be from a well-known performer in a performance with very limited audience or in some remote area. It could also be a piece that gets hidden inside a long RTP ragamalika. An example of the latter is Mali's rendering of thODi in the following extract from a RTP with ragamalika:
https://www.youtube.com/watch?v=kz679WN ... rt_radio=1
Enjoy!