Scott Disick and Kourtney Kardashian Run into Sofia Richie at Nobu

Here's the thing about Malibu ... as fancy as it can be, it's also really just kinda a one-horse town, which Scott Disick learned all too well Friday night when he, Kourtney Kardashian and Sofia Richie all dined under the same roof.

Scott and Kourtney hit up Nobu in Malibu, a favorite of celebs these days. It seems to be his go-to place. Thing is ... it was also his go-to place when he was dating Sofia for several years after his breakup with Kourtney, and she was there too.

Our Kardashian sources say Scott and Kourtney are friends with lots of history and great co-parents, but their relationship is strictly that and no more.