Free Starbucks anyone?
Most places do not require an incredible burden of proof in most cases. If you say something was taken, they will replace it most of the time. This applies to food and drinks and is mostly it. Other more expensive items require a bit more proof.
At places like Starbucks, you can get away with saying your drink was stolen so you can get another free drink for your sidekick on a hot day. Not that it makes it right, but I am sure it happens more than you know. Maybe that will put your mind at ease a bit?