As a guy who sells this type of product all day long, I have a few questions for you.
Are you sure it shipped?
How much control do you think a seller has on an item once it has left their building?
Are you aware that UPS, etc. misplace, damage and loose packages and there is nothing the seller can do about it?
Are you sure the correct address was on the package?
We ship ammo with Adult Signature Required. Did Double Tap do that and was someone there to sign for it?
Finally, were your communications with Double Tap as filled with anger as your post?
They provided great service before so something must have gone wrong this time, ie. illness, injury, death, building burned down, etc. Should they have gotten back to you? Yes. Is it the end of the world? No.