no warranty?

The official website further says:

iPhone 7, iPhone 7 Plus, iPhone 8, iPhone 8 Plus, iPhone X, iPhone XS, iPhone XS Max, iPhone XR, iPhone SE (2nd generation), iPhone 11 Pro, iPhone 11 Pro Max, iPhone 11, iPhone 12 Pro, iPhone 12 Pro Max, iPhone 12, and iPhone 12 mini are splash, water, and dust resistant and were tested under controlled laboratory conditions; iPhone 12 Pro, iPhone 12 Pro Max, iPhone 12, and iPhone 12 mini have a rating of IP68 under IEC standard 60529 (maximum depth of 6 meters up to 30 minutes); iPhone 11 Pro and iPhone 11 Pro Max have a rating of IP68 under IEC standard 60529 (maximum depth of 4 meters up to 30 minutes); iPhone XS, iPhone XS Max, and iPhone 11 have a rating of IP68 under IEC standard 60529 (maximum depth of 2 meters up to 30 minutes); and iPhone 7, iPhone 7 Plus, iPhone 8, iPhone 8 Plus, iPhone X, iPhone XR, and iPhone SE (2nd generation) have a rating of IP67 under IEC standard 60529 (maximum depth of 1 meter up to 30 minutes). Splash, water, and dust resistance are not permanent conditions and resistance might decrease as a result of normal wear. Do not attempt to charge a wet iPhone; refer to the user guide for cleaning and drying instructions. Liquid damage not covered under warranty.

The iPhone is not advertised as waterproof. It is advertised as water resistant, and it clearly states in the specs and the warranty that water damage is not covered. You also didn’t take it to Apple or an Apple authorized service provider, because they would not have charged just to dry it out. They actually would have told you to dry it out. And a non-Apple shop would not have honored a warranty anyway. There’s a good chance the repair will be temporary, and the phone will fail at some time in the near future, because water damage is generally progressive.

You may find this informative: Understanding Water Resistance

Liquid damage is not covered by the warranty.

No iPhone is advertised as "waterproof".

They are water resistant. Not the same thing.