Touch function repair after falling to water (3 months later)

Oh it could be a couple of things

First the screen itself.

Second the touch circuit inside you phone.

Either way once the phone dries it starts corroding on the inside.

The least that you could do is tear it down and clean the board and connectors with 90%+ IPA.

Then reassemble and assess.

Or send it to a pro shop for pro cleaning if the board is too corroded.

However if it was me, I wouldn't spend time and money on a liquid damaged phone unless the damage is very limited since otherwise they tend to fail over time, one function after the other as corrosion eats away at them or the corroded and weakened joints -even after cleaning corrosion- start failing.