My wife later told me that she noticed that the men behind her put their backpacks underneath the pew, directly under her bag. She later noticed that her bag was slightly opened and the zipper in a different position from where she left it. As soon as she looked behind her, the two men behind her and the couple beside me stood up and left.
Even though we spoiled the thieves' plan, we should all realize that they are still demons, defiling even Sunday Mass! Nothing is sacred with thieves. Thieves are scared of nothing.