He did spend a lot of time in his bedroom. Once at a Barry Harris show at the Vanguard, Barry told a story about Monk. Both were living in the baroness' house in Hackensack. Barry said he was practicing a tune for about 3 hours. Barry said he paused before playing some more. When he started up again, Monk opened his bedroom door and yelled "Shut the fuck up. You know it enough"
When I was in the 11th grade, I was in the school band. I had a friend in the band who's mom was Monk's niece. He told our music teacher Monk was his Mom's uncle. Our teacher asked if he could call Monk and see if he would come to the school. My friend's mom called, but he wouldn't come out of his bedroom to talk on the phone. I assuming the woman on the the other end of the call was Nica, but don't know for sure. This was in 1980.