As I discuss in this question, by far the most popular school of Hindu philosophy is the Vedanta school. But there are five other Astika or orthodox schools of Hindu philosophy: Purva Mimamsa, Samkhya, Yoga, Vaisheshika, and Nyaya. My question is about the Samkhya school, founded by the sage Kapila. Now in Adhyaya 4 of Kapila's Samkhya Sutras, one of the defining texts of the Samkhya school, Kapila discusses various scriptural stories which illustrate different Samkhya teachings. In particular, here's what he says in Adhyaya 4 Sutra 2:
(Discrimination results), as in the case of the Pishacha, even though the instruction was for the sake of another.
Here is how Vijnanabhikshu interprets this Sutra in his commentary on the Samkhya Sutras:
Even women, Shudras, and the like may attain their end by hearing the instruction of one Brahmana by another Brahmana; with a view to show this the author exhibits another story. Although the instruction in regard to the Tattvas or Principles was being deluged by Shri Krishna for the benefit of Arjuna, discriminative knowledge was produced in a Pishacha standing nearby. Similarly it may be in the case of others also. Such is the meaning.
My question is, what is the story of the Pishacha who overheard Krishna telling Arjuna the Bhagavad Gita? For those who don't know, Pishachas are a race of demons described in Hindu scripture.
The only similar story I've heard is the one told in this book and other places, about Hanuman overhearing the Bhagavad Gita and Krishna cursing him to turn into a Pishacha. But I'm not sure if that story has a scriptural basis, and in any case the two stories aren't quite the same.