Margaret it has been a Bonza day here South of Brissie the heavy shower we got this morning ( Friday ) left 11mm in the Rain Gauge and we have had a few very light showers since. Yes those winds can be a killer I too hope that its cools down for you all there and its rains very soon. GH I wonder if you are getting any of this beautiful rain also, sure hope so .....Cheers..MM.

"There is no longer any water showing up on the sheets of paper. Can I eliminate the possibility of a leak in the pipes?" That may indicate that there isn't a leak when the shower valve is off. Leaks behind the wall are rare, but they do occur. You could troubleshoot leaks behind the wall by unthreading the shower head from the arm that comes out of the wall. Crack the shower valve so water starts trickling out of the arm, then close the valve. Now thread a 1/2" cap on the arm (in place of the shower head) and turn on the shower valve. That'll pressurize the plumbing between the valve and the cap. Leave the supply valve on for a while. If water starts showing up within a few hours or the next day, then there may indeed be a leak behind the wall. You can try to get a visual on it at the same time be sliding the shower head escutcheon plate off the arm, that'll allow you to put eyes on the union that the shower arm threads in to. You can also remove the escutcheon plate that covers the shower valve. With the shower head removed, the shower arm capped, the two escutcheons removed, and the water ON, you may be able to see or even hear a mist or spray from any faulty unions. If visibility is restricted, you can also poke a Q-tip or something like that into the holes and see if it comes out wet. But again...leaks behind the wall are rare. I'd be interested in finding out if the floor membrane itself is sloped to the drain. Many installers who use CPE or CPVC membranes improperly lay the membrane flat on the floor, then set sloped mud on the flat membrane and tile on the sloped mud. However, it's a code requirement that the membrane itself should be sloped. Lastly...sometimes these weird water things can disappear on their own over time. Fresh mud beds become wet with their first use, and on these forums we've had a few instances of water behaving badly while the bed saturates over the first few uses. Good luck with it.

What brand and type of grout is it as not all grout requires sealing?

The musty smell is from mold - some of which may make you ill. Good that you stopped the leak but without further investigation you don't know how much hidden damage there is. There are ways to remediate the smell but even a slow leak can damage underlayments and structures.