My screen stays black

Dan, rice is a great first aid but it will not prevent or fix corrosion. Since your phone went through the wash, I am certain that the alkaline wash water will cause corrosion down the road. I suggest that you no longer try to turn it on or try to charge it. Disassemble it using this guide and properly clean it. Use this guide to clean it. It was written for a 3G but all the points are still valid for your phone as well. Always check your board for any missing, burned or otherwise damaged looking components. After that replace the battery, reassemble your phone and re-evaluate for any problems. the backlight for your phone is contained in the front display panel, and the backlight control is part of your logicboard, IC and coil are on the board. So, if nothing else I would replace the LCD after properly cleaning the phone. If that does not work, you may have to replace the IC and coil and hope that there is no other component that was damaged by the water. Hope this helps, good luck.