Unfortunately, the worst thing you could possibly do was to let water fester and corrode your phone for a few days while it was sitting in rice. The water is in the phone, on the logic board and under the shields, even under the IC's. The rice is nowhere near where the water is...it cannot help your phone.
When the water is allowed to evaporate, it leaves deposits of minerals that can cause short circuits or corrosion. Heating or powering the phone accelerates the process. The water needs to be displaced, not heated and evaporated.
Sorry about that, now on to helping you.
- Open your phone and remove the logic board (follow this guide)
- Inspect the logic board, especially around the connectors and look for corrosion.
- Inspect both sides of the board. Unfortunately, 80% of the board is covered in shields. That's usually where the damage is occurring.
- Put your board in a container with >90% isopropyl alcohol and let it sit for a while.
- Use a soft brush, like a toothbrush and lightly brush away any corrosion you see.
- Rinse in alcohol and repeat.
- Let it air dry for a day.
- Re-assemble and hope for the best.
- Use a tool like 3uTools to flash the firmware as it may be corrupted.
- You should also consider getting a new battery
A professional repair shop that does water damage repair may be able to recover your phone or the data because they have access to pro-level ultrasonic baths and specialized cleaners as well as the skills to troubleshoot your board.