In my experience, such situations are rather rare. The only significant such encounter I can recall is one in which i literally "set the table" by storing succulent sweet rolls inside the tent in anticipation of a morning breakfast. Storing food outside the tent keeps the critters away.

Really good thieving critters make little or no noise. One such master thief was a silent coatamundi who hung out near camp sites on Baboqivari (Arizona). He or she was in and out of your hanging pack in absolute silence in just a few seconds.