phone stuck in headphone mode after repairs

This is a belated answer so hopefully it can be of use to folks who search for and find this question.

These issues are most likely all related to the water damage. The water gets inside the phone, on the logic board and under the shields, even under the IC's. The real problem is the mineral deposits that can cause short circuits or the corrosion that is taking place as the water evaporates. Leaving the power on the device accelerates the process. The longer you let a phone sit in rice, the more time you are giving corrosion to damage your logic board. The saltier or harder the water is, the more damage will occur. The water needs to be displaced, not evaporated.

The proper way to treat a wet phone is to do the following:

• Open your phone and remove the logic board
• Inspect the logic board, especially around the connectors and look for corrosion.
• Inspect both sides of the board. Unfortunately, most 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.