how can i fix my bathroom digital scale?

give this a try after which if it dosen't cure it then throw it away.
Take the unit batteries out leave them out to dry lay the scale on a radiator set low so if unit is plastic too hot it may cause deforming of the plastic. or you could lay a towel on the radiator then lay the scales on the towel on radiator at med to high for about 1 hour. Try them out. if no display of numbers do it again for another hour if no display it could be the water damaged or shorted out the units printed circuit so throw it away and buy another. Get mechanical one not electric digital, you won't have that problem of water again.
I did this dryout method with a caravan mover remote control unit I left out in the rain and it worked again. Tip get a clear( see through) plastic bag if you do get another display one slide it in the plastic bag and it won't get water on the scales and can be used while in the bag

Bob
March 2013