I accidentaly swallowed a large piece of aluminum foil (AF). It was a coffee bottle seal, and thicker than regular kitchen AF. What should I do?

No to worry. This will get churned and crushed (but probably not torn) by the normal action of your GI tract Almost everything small enough to be swallowed can be handled effectively by this efficient system. You will probably find it exiting the other end in 20-40 hours depending upon the activity of your digestion.