It's a water marker, not water sticker. It's at the bottom of the headphone jack, white circular marker. It will turn half red if there's any contact with water. There's one more on the bottom connector as well but not visible to the naked eye.

TS complained that he got conned the first time when buying the phone with broken earpiece, well TS should check the phone thoroughly before purchasing it. There are possibilities that the earpiece is not functioning because of water sipping thru the earpiece. If that happen then the water marker won't be activated.

@crxr
Is the touch screen working before you start dismantling the phone?