My phone registers headphones when none are plugged in. (LG Stylo 4)

Hi,

Hopefully you may only have to replace the headphone socket

As you know water and electronics and electricity are not a good mix.

The water causes corrosion and provides circuit paths for the electricity which were not in the phone's operating design and could damage the components. The corrosion starts immediately and is ongoing until it has been properly cleaned away

Rice does not fix the problems caused by corrosion

Rice is for dinner, not for repair

First do not turn on your phone and then you need to remove the battery as soon as possible from the phone to minimize any further damage.

Then you need to dis-assemble the rest of the phone and clean all the affected parts using Isopropyl Alcohol 99%+ (available from electronics parts stores) to remove all traces of corrosion and water. Do not use "rubbing alcohol" as in some cases this is only 70% IPA or less, can contain scents and is not as effective. If you do have to use it, check the label to verify the amount of IPA. The higher the percentage of IPA and the less “other” ingredients, the better.

Here is a link that describes the process.

Electronics Water Damage

As always with electronics, especially surface mounted PCBs be gentle when handling and especially when brushing away the corrosion. You do not want to remove any components from the board.

Hopefully after you have done all this the phone might possibly work correctly again.

Here is a link to a video that shows how to replace the screen in your model phone. I realize that this is not the problem with your phone but it is useful as it shows how to open the phone so that it can be inspected and cleaned.

If this process seems too daunting, take your phone to a reputable, professional phone repair service, experienced in liquid damage repair and ask for a quote for a repair. If you decide to do this, do it sooner than later.