Matsya Purana — The Syamantaka Jewel Episode and the Vrishni–Sainya Genealogies
हत्वा ऋक्षः प्रसेनं तु ततस्तं मणिमाददात् अदृष्टस्तु हतस्तेन अन्तर्बिलगतस्तदा //
hatvā ṛkṣaḥ prasenaṃ tu tatastaṃ maṇimādadāt adṛṣṭastu hatastena antarbilagatastadā //
Having slain Prasena, the bear then took that jewel. And Prasena, unseen by anyone, was killed by it and at that time lay hidden within a cave.
Nothing directly—this verse is part of a royal narrative about a stolen jewel and a hidden death, not a Pralaya (cosmic dissolution) teaching.
It implies the need for careful investigation and justice in cases of disappearance, theft, or suspected wrongdoing—royal duty (rājadharma) includes uncovering hidden causes and restoring order.
No Vastu Shastra or ritual procedure is stated; the only concrete detail is the setting of a cave (bila), used here as a narrative element of concealment.