Radha IS mentioned in the Srimad Bhagavatam

Sometimes it is argued that the person of Radharani is imagined or one of the misconstrued elements of bhakti, that Krsna needs a female companion, and so on. But Visvanath Cakravarti, explaining the twenty-eighth verse of the thirtieth chapter of the Tenth Canto, tell us otherwise: “The sage Sukadeva Gosvami has tried with all endeavor to keep Her name hidden, but now it automatically shines forth from the moon of his mouth. That he has spoken Her name is indeed Her mercy, and thus the word aradhito is like the rumbling of a kettledrum sounded to announce Her great good fortune.”