Where's the Keys????? Quack!!!
The nose ... or in this case .... the bill knows.
Here at the duck farm, one way to keep track of keys is to always put them in the same place. A great place is on the duck's bill.
When the keys are not on the duck's bill, you know that someone has ducked out for a spell.
Using a french accent, the situation is described, "Zee kiss are on zee bill."