For all we know, he literally found Mister. Murphy lives in Bucktown as well, after all, and Mister likes going off on nighttime rambles. Assuming that Bob can teleport-dash like Ghost Harry, I’m not too concerned that he might have found a vessel in that time.
I mean, we know that Bob survives; Jim says that Harry’s going to have to have a talk with Bob to stay away from Bonnie. So either Butters’ apartment is within teleport-dash range, or Bob found a kitty to hang out with.