I had the same strop, do the same thing. and it was not kept in the bathroom. What I did was to soak it in Neatsfoot oil, and let it sit overnight. I then soaked it again. Wiped off the excess, and pressed it between 2 boards with a few pounds of weight on it. a few days later, the excess oil had soaked into the boards, and the leather was nice and flat.

I have not yet put it to use, so only time will tell if this truly worked, or just looks like it did. And it did make the leather much darker than it was before.

Had to wash the linen side out after too, as it got oiled. Duh!