Hi @stereoshock,
The phone has an IP52 rating, using the Ingress Protection rating system. The dust rating is 5, and the water resistance rating is 2 (protected from water spray less than 15 degrees from vertical). This doesn't mean that is waterproof.
How long did you allow it to dry before connecting the charger?
Bit confused as to the time line as you said "in the morning when the message disappeared, I connected the charger and went to bed, but when I got up in the morning I found that the phone was turned off".
Check to see if the [https://www.verizon.com/support/knowledge-base-235044/|liquid damage indicator] has changed colour.
If it has or even if it hasn't, since there has been a message regarding water and now that it doesn't charge (does it still turn on?), ''***do not try to charge or to turn on your phone*** ''and then ''***remove the battery as soon as possible*** ''from the phone to minimize any further damage.
''The impurities in 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 is completely cleaned away''
In any event i.e. if it still turns on then perhaps only the charging circuit has been damaged, or if it doesn't turn on you need to dis-assemble the rest of the phone and clean ''all the affected parts'' using ***Isopropyl Alcohol 99%+*** (available at electronics parts stores) to remove all traces of corrosion and water. If possible do not use "rubbing alcohol" as in some cases this is only 70% IPA or less, can contain additives 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 the better
Here is a link that describes the process. [[Electronics Water Damage]]
As always with electronics, especially surface mounted pcb be gentle when handling and especially when brushing away the corrosion. You do not want to remove any components from the board. Remove the shields that may be covering some components as the water may have got in under there. The ends of any flex cables and their connectors need to be cleaned as well
Hopefully after you have done all this the phone ''might'' possibly work correctly again.
Here is the ifixit [[Topic:Google Pixel 4a 5G]] that may help.
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''.