i was reading about this recently, and (i wish i still had a link) read that rather than, like, hanging onto a yeast infection from a female partner and then reinfecting her with it, a male might develop one due to exposure to the excessive yeast triggering his own body to overgrow it (although this happens rarely, like smallstar alluded to). i'm not really explaining it well, but it's a different concept from "catching" a yeast infection in the way we think of catching a viral or bacterial infection, so that could be the issue with what the nurse said.

also, oral thrush can be acquired a zillion ways other than oral sex with someone who has a yeast infection, and that's probably one of the least common ways to transmit it, anyway! just throwing that in.