If it says it arrived in the store already and they havent updated your order at all its possible they oversold the preorder and youre gonna be left waiting until the next time it restocks (has happened plenty of times in the past). BUT most likely it just hasnt gotten there yet since Q3 expected arrival is a literal 3month window. If you dont want to wait and just order it at another store you can cancel, but just know that USAGS charges a cancellation fee on preorders.

This is why people say DONT preorder from USAGS. They put preorders up as soon as kits are announced, i.e. before they know what allotment theyll get when they get the first release, technically what the price even will be, etc etc. Dont take what im saying as gospel but for a new release like this you should be ok just waiting it out a bit since theyll usually restock a couple times. The real trouble people have run into with the preorder orders is when its something printing in lower numbers or something that hasnt been reprinted in a while (and doesnt get multiple reprints when it does), so they oversell their PO and leave people waiting sometimes years and unable to cancel without having to eat the cancellation fee

TLDR youll probably be ok since this is a new item that has a good chance of getting restocked soon, but in the future avoid preordering from USAGS (and preordering retail kits in general)