“”They should have (and I suspect most do) signage indicating that all sales are subject to verification by receipt on exit. “”
You are making stuff up on the fly. There wouldn’t be much point to this thread if all the stores had legal postings instructing shoppers that they would be searched after completing purchases.
Most of the legal issues have already been covered on this thread, if you have some legal information to post do it, don’t vaguely claim it exists, and send us off to scour the law books for it.
An Offer
An Acceptance in strict compliance with the terms of the offer
Legal Purpose/Objective
Mutuality of Obligation also known as the meeting of the minds
Consideration
Competent Parties
There are hundreds of thousands of cases which have been decided based on these basic requirements. This is first semester business school stuff. Accept it or ignore it as you will. The world is not based on your concept of what your 'rahts' are.