This is funny. Is this analogous to finding a wallet on the street and returning it (in my locale: and getting a finders fee), or is this analogous to taking a wallet from a drunk sleeping person (morally dubious), contacting them the day after to return the wallet, or is it just stealing per se.

Where I live it's only theft if there is an intention to unlawfully take ownership of the good. As an example, forgetting to pay in a supermarket lies exactly on that boundary. Take a cart or hide a product and you won't get away. Try to pay, payment fails and you don't notice, walk away and get apprehended and you might convince the judge that you had no intention to unlawfully take ownership.