A more thorough explanation:

Lost is an adjective that describes something that is no longer in the possession of its owner and cannot be found even after a thorough search. It can also refer to a person who is missing. In parliamentary law, it describes a motion that has been rejected and not adopted.

• My keys are lost, and I can't find them anywhere.
• The ship was lost at sea, and no one knows what happened to it.
• The parents reported their lost child to the police.
• The motion to increase taxes was lost in the parliament.

The first two examples illustrate the first definition of lost, where something is no longer in the possession of its owner and cannot be found. The third example shows the second definition, where a person is missing. The fourth example illustrates the parliamentary law definition of lost, where a motion is rejected and not adopted.