Meet Bob. Bob purchased something and elects not to print/collect a receipt from the self checkout till. The security then accosts him suspecting him of not paying for it and he insists that he did, so the security asks him for his receipt. He says he doesn't have one, so security asks which till he used to check out and pay. He doesn't remember but reckons it's one of those middle three and security asks him to wait while they check those three for the transactions.

Bob meanwhile is in a rush to get somewhere and would like to leave with the goods he has in fact already purchased.

When does shop keeper's privilege entitle shops to makw such impositions on one's time and movement?

EAW specified all jurisdictions welcome.