Retailers are not LEOS. The 4th amendment only applies to government. Its like crying for your first amendment protections here if a moderator zaps one of your posts. The constitution is irrelevant until the government gets involved.
Just who do you think is asking the Retailers to submit the informaiton, and to whom do you think the forms are sent?
While true that the constitution only protects citizens against state action, and not private action, when a retailer is required by the government to collect information and report upon its customers, that IS state action.