I wouldn’t think of it as a blessing or as a test from God. I would think it should go back to the owner. Otherwise you could be guilty of theft, and of committing a mortal sin so that you become a lost soul.
I would report it to the police too. I also think such a person would be legaly obligated to give it to the police, and not only report it… I believe though that according to U.S.law that if the owner does not come forward, it would belong to the finder. And so before turning it over to the police, I would talk with a lawyer.
A previous poster is correct about taking into account the circumstances. Several years ago someone the the Southwest U.S., I believe, found a bag with hundreds of thousands of dollars with a gun on top in the bag. The police advised him not to claim the money at all, apparently because it could have been money from the sale of drugs, perhaps, and he would have been the target of the criminals whose money was in the bag.
I also recall that a bag of a bank’s money fell onto the street from an armored car. That is another situation entirely, and since the bag had the bank’s name on it, clearly it should have gone straight back to the bank.