I just bought a new house and three days in, the diverter button in the shower started failing while taking a shower (a few days later, it started totally popping out of the wall). At first I thought there was some weird timer, but then I realized that the previous owners basically installed a shower/tub faucet on a shower only unit (which means the valve is for a shower/tub also). The short term fix is tightening the diverter button w an Allen wrench, but that doesn't even really work bc the valve is threaded and the diverter button doesn't screw in. It also doesn't stop the button from popping out enough to stop the water flow. My head is about to explode because a plumber said we'd have to basically take out the wall to replace the entire valve. The plumber said we could super glue in the diverter button, but that seems shoddy at best.... Is there anything we can do short of knocking down part of the wall? I read this on a blog and was wondering if there's any safe way to "cap" my valve that won't result in potential bursts/leaks, etc.:

“To further confuse you, it’s absolutely possible to make a tub and shower faucet work exclusively as just a shower faucet. This is especially true if the diverter to make the water go to the showerhead is in the actual tub spigot. All your plumber has to do is stub a dead end pipe with a cap on the outlet in the faucet that’s supposed to feed the tub spigot. I’ve had to do this on occasion when the faucet model and trim that a customer wanted didn’t come as a dedicated shower-only faucet.”