All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The ruling about this umbrella if it has a value to which a person’s heart may be attached is that it should be made known as soon as you found it for a period of a whole year, and then [if its owner does not come] you may benefit from it while you guarantee its price in case its owner comes one day after that. Therefore, if you did not make this umbrella known, then you should make it known now for a period of one year if you do not predominantly think that it is useless to make it known now. In which case, you may benefit from it provided you guarantee its price.
However, if the umbrella has no value according to the customs, then it is permissible to own it without making it known.
For more benefit, please refer to Fataawa 88519 and 84691.
Allaah Knows best.