Soldato
Which is a tricky business.It's the same with PCSO's, they have to observe the crime on which they can make a citizens arrest and I believe only hold your for 20 minutes in which time an officer will arrive. They cannot hold you on suspicion of a crime.
I don't see how anything in the OP indicates anything remotely like Attempted Robbery, more like Deception, Fraud or Theft... Not know what exactly the store/police thought she was doing with the top.