I bought a house last year, and in several rooms I could not find studs on any interior walls. Baffling. I'd find screws, but then when I'd drill I'd find no stud behind it. Weirdest thing.

Finally realized somewhere along the way drywall sheets were hung over the old lath and plaster walls, so the studs are far enough back to be undetectable with magnetism. The screws are just kind of random and only sink into the previous wall, not the studs. I've considered pulling off the drywall to see what's actually going on back there (I assume water damage, as many places in the house have water damage), but then I'd have a bunch of drywall to replace, in addition to everything else that needs doing.