> I bet all are tracked and cross-referencable with the requestor
In theory they are not. The individual store is supposed to keep a paper record of the sale and the background check result so that they can be audited, but that is meant to be the only record.
Of course who knows what is being done to illegally capture the data.
A number of US states do not require background checks when it's resident-to-resident (I live in one). It's common to trade a bill of sale between parties but the paperwork stops there, and this paperwork is technically optional.
It sounds like mostly nothing is being done considering how slowly police gun trace requests are performed via a paper database search, but things could have changed since 2016.
In theory they are not. The individual store is supposed to keep a paper record of the sale and the background check result so that they can be audited, but that is meant to be the only record.
Of course who knows what is being done to illegally capture the data.