At SB 3.9.37 the Lord says: 'tubhyaM mad-vichikitsAyAm AtmA me darshito abahiH / nAlena salile mUlaM puShkarasya vichinvataH' — for your doubt about Me My own self was shown to you, as to one seeking the root of the lotus in the water by the stalk. This is the answer to the failed search of SB 3.8.19.
The Cosmic Lotus
ब्रह्म-कमल
Also known as Loka-padma (the world-lotus)
The cosmic lotus is the world-lotus that arises from the Lord's navel and on which Brahma appears. At SB 3.8.13 the purpose within the Lord, finer than rajas, struck by the guna that follows time, splits open from the region of the navel; at SB 3.8.14 that lotus-cup rises suddenly and lights the vast water 'arka iva', as the sun does. At SB 3.8.15 Vishnu enters that world-lotus and in it the maker becomes self-born. At SB 3.8.16 Brahma stands on its pericarp and obtains four faces; at SB 3.8.18-19 He searches for its root and does not find it; at SB 3.8.32, at the resolution, He sees that navel-lake and its lotus.
Śrīmad Bhāgavata Mahāpurāṇa 3.8.14 — Sanskrit Wikisource (pinned chapter page; Devanagari from the cross-validated transcription in validation/sanskrit_skandha3.json)
At SB 3.8.13 the purpose within the Lord, finer than rajas, struck by the guna that follows time, splits open from the region of the navel. At SB 3.8.14 that lotus-cup rises suddenly and lights the vast water with its own radiance. At SB 3.8.16 Brahma stands on its pericarp, moves about in the sky and obtains four faces. At SB 3.8.19 He descends through the stalk to find the lotus's root and does not find it.