The adjective lost describes anything that can't be found, like your favorite pair of sunglasses that you left on a table at the library and never saw again.
Beloved hand-knit scarves can be lost, and so can wandering pet goats. A person can get lost in the unfamiliar, winding streets of a strange city. You can also describe someone as lost if they're confused or desperately in need of some kind of help. The origins of the word lost come from the Proto-Indo-European leu, "to loosen, untie, or separate". The meaning "to be defeated," like when you've lost a game or lost a battle, came later, around 1530.