finder
n. countablen. a person who discovers something that was lost or hidden. You use this word for someone who finds an object or even a new piece of information.
n. a person who discovers or locates something, whether by chance or through a deliberate search. Often used in the context of legal or social rules regarding lost property.
The finder of the lost wallet returned it to the owner.
The museum offered a small reward to the finder of the ancient coin discovered in the field.
In many jurisdictions, the finder of lost property has a superior claim to the object against everyone except the rightful owner, provided they take reasonable steps to locate them.
From Middle English findere. By surface analysis, find + -er.
Commonly appears in the idiomatic phrase 'finders keepers'.