I called Roy, our contractor, first thing Friday morning. He was mystified, but went to check it out. When he called me back a few hours later, he reported that the stench was totally gone. He spent a few good hours there, talking to his plumber, checking vents, and actually sniffing various drains, but nothing.
Our working theories are: A) We experienced a one-time backup. This is not too far-fetched, given that we’ve had sewer issues in the past and the Roto-Rooter man has not paid us a visit in over a year. Though a backup is usually accompanied by something actually coming up out of the drain. Maybe we got lucky on that front, though that hardly feels like the right word.
Theory B is that the kitchen drain, which backs up to the bathroom, is sucking the tub trap dry. Maybe we accidentally tampered with it while installing the dishwasher. But we’ve run the dishwasher plenty, and only had one instance of stench.
In any case, all we can do is be on the lookout (smellout?) for a recurrence. Of course, we are both so paranoid now that we’re smelling phantom odors everywhere (easy to do in a bathroom). We had one false alarm already that turned out to be an old washcloth.
In any case, I’m beyond relieved that we may not have to rip out any tile or move any appliances. That would’ve stunk.