The story of Buddha Vipassi is told in DN 14, and the first people to go for refuge do it indeed only to the Buddha and the Dhamma, as the Sangha isn’t there yet:
DN14:3.12.4: Ete mayaṁ, bhante, bhagavantaṁ saraṇaṁ gacchāma dhammañca.
We go for refuge to the Blessed One and to the teaching.
If you want to find a Pali quote on SuttaCentral, I think it is recommended to use the ṁ, not the ṃ, as the former is what is found on SuttaCentral.