How do I get a code for a game I bought when the receipt got thrown out with the code on it?

It will be in the email that you have set up on file they will email it to you then you will have to give the code to curbside pickup or if you go inside to customer service.

You will get if you have account with best buy or redeem online going to website or customer service support mostly in your receipt they give you all details

If you paid cash, pretty much nothing. If you paid using a debit card or credit card, go to the store and ask for a copy of the receipt. You need to know what date you purchased it though.