If you get intercepted by police in a parking lot, just say
You: 'Is there a problem, constable?'
Cop: 'No, I just want to ask you what you were doing inside'
You: 'I have nothing to say, constable; am I being detained or under arrest?' (don't lie or they are going to corner you)
Cop: 'No'
You: 'Can I go now? Have a nice day, constable'
If he says that you are being detained, you have the right to remain silent. You have the right not to incriminate yourself. You can incriminate yourself even if you've done nothing wrong. What you say will be used against you in a court of law, in spite of any assurances they may give you, especially if they try to make a deal with you, and it will cost you a pile more money for your lawyer (at $700 an hour) to extricate you from the mess you created for yourself. Police are not your friends; their job is to enforce the law, and they will use every trick in the book to get an arrest and conviction.