Just guessing... The table can't sense a chip leaving the area, but can sense one crossing a boundry line. Imagine a wire loop, under the carpet. If a chip crosses it, the alarm goes off.

So you hand the waitress a chip and when she sets it off, you exit the area. LOL

Alt. plan "B" you and the patsy (co-conspirator), leave the table. Patsy stands past the line, fishing for the one chip that he forgot, while you make tracks out of the area with the real booty!