money found on floor of coffee bar

Who owns the money?
I went to a coffee bar and ordered a latte from the ordering counter. As I was putting my change away in my purse, I noticed a $20.00 bill lying on the floor at my feet. It was not one of my $20.00 bills. I looked around to see if there was another customer waiting for their order who might have dropped it. I did not see anyone waiting for an order, so I kept the $20.00, following Snoopy's Law: anything that falls on the floor is mine.
My husband says that the $20.00 belongs to the coffee bar because they pay the rent, utilities, etc. to run their business, and I was on their turf, so they should get the money.
What legal principles apply here? The coffee bar in question is in California.

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