Why is my iPhone 6s screen not responding?

HI, my friend accidently dropped her iphone 6s into the toilet bowl. She immediately tried putting it in rice to let the water drain out. After that, the phone turned on but the phone did not respond to touch. The screen looks fine and the home button and power button are working but when i touch the screen, there is no response. So, i was wondering is there a problem in the digitizer or logic board or anything else? Is there any way i can check what is wrong or would an lcd replacement help?