Completely Destroyed iPhone 6
Warranty from Apple doesn't cover accidental damage.

If you have insurance from the carrier or AppleCare plus, they will pay some or all the costs to repair it.

Put the pieces in a ziplock bag and call Apple or visit a retail store to get a quote for replacement in writing so you can provide that to the carrier and/or insurance company. Depending on how badly you need a replacement, you might pay for Apple's repair and check coverage later.

Best of luck and have a look at cases like life proof and otter box that might help in bad situations if you decide not to insure the replacement.