DOP - disappearing object phenomenon - is a relatively common phenomenon in which an object disappears from view and later inexplicably returns. For example, a person puts their car keys on a kitchen counter, where they are always kept. When the person goes to get them, they are gone. A thorough search turns up nothing. Later, the keys are found on the counter where they were originally put (or some other obvious place.
It's difficult to document a genuine DOP occurrence because people can be careless, simply misplace things or be forgetful. But there are many compelling stories from people who are certain they looked for the object in the place that it later appears. In some cases, people audibly call out for the object to be returned - and it is. In some rare cases, the missing object has actually been seen materializing out of thin air. It is also known as the "borrower" phenomenon. It may be related to poltergeist phenomena.