Ethics gut check: Found lotto ticket that wins, do you try to return it to the owner?

Here is your scenario for this ethics gut check, you are at the library and a woman places some books on the ”donate pile” and leaves. One of the books she placed there catches your eye and you grab it to take a peek. A lotto ticket falls out for the draw four days ago. You look for the woman but she is long gone. You notice some of the books say “if found call Alfred at bla bla number”, but the number area code is outside the area you are in. Out of curiosity, you have the numbers checked. Then all hell breaks loose, the clerks are all excited. They tell you that you have won 21 million dollars. What do you do, keep mum about how you got the ticket and go cash it in, or do you confess that you did not purchase the ticket and try to find the woman who left it in the book?