I agree with the catechism, of course.
I think it’s the factor of “piggy bank” that’s ping-ing my mind to think there’s a close familiar relationship involved here, where a sort of default consent might
potentially be pre-established. Like siblings, or friendly roommates. Also, I know some people refer to something as a ‘piggy bank’ when it’s really just an open dish with loose coins in it, so not necessarily something that’s ‘broken into’ so much as sitting open on a dresser, where someone might have been invited previously to ‘dip into it’ so long as they filled it back up.
So making a bunch of assumptions here because the OP hasn’t clarified the relationship, the presumed consent status, or the situational context…
It seems hypothetically possible to me that the circumstance in question could be two close friends who are roommates, and one keeps a pig-shaped (
) dish of coins on top of a dresser. He’s given his roommate permission to use coins from this dish on past occasions, and the roommate has always paid him back. Now one day, the coin-owner is out of the house at work, and the roommate is rushing around getting ready for a crucial job interview… and suddenly realizes last minute they don’t have the leftover change they thought they had, for the bus. They used it on laundry last night. There’s no way to contact the roommate who’s at work (whoops, he’s down a mine shaft!), but they’re
certain that if the roommate was right in front of them, he’d say: “Oh my goodness, of course! Grab the money and run! You need to catch that bus!”
This is the kind of proportionality I’m thinking of. Not necessarily life and death, but a reason the
owner would be expected to consider proportional under the circumstances (like needing coins to catch a bus to a job interview), that the hopeful borrower might know them (and their past interactions) well enough to reasonably predict.
Like others have said, I’d presume that no matter what, the ‘borrower’ would tell the owner as soon as possible with an apology and also the full returned amount. I’m just also presuming that there could be many circumstances where a person could really reasonably expect that a given individual would say “Yes,” and might even feel hurt if they later find out someone assumed they would have said “No”. Very much depends on the relationship and past expectation-setting, I think.
Just my two cents though.
(Also maybe I should be adding more directly: if none of what I’m saying above applies (re: presumable consent, urgent need), then yes this is theft. I just made my initial comment requesting more information because I don’t think the OP gave us quite enough to make a definitive assessment one way or another.)