Why would you leave it on the counter while you were sitting somewhere else? Did you just forget it there?
Usually after a purse theft you should check the trash bins near the area because many times the thieves will dump it, but because it's so small they might not have. If it was on the counter it seems to me that an employee took it. When you cancel the card see if they can tell you what charges were on it, you could also visit those stores and ask for the security footage. But unless you know the person, the video isn't much help.
Yes, I forgot it. I was carrying two drinks so my hands were full. I was too distracted trying to prep the cups for transport. I did talk to the employees and left a note for the manager. I will ask about the security footage. That is a great idea.