Yes, a wrong act is still wrong even if nobody ever knows about it. An action is wrong if it brings about some kind of harm to oneself or to others. Whether or not a third party is made aware of that harm is insignificant, as harm has still occurred. As long as the individual does not have some sort of mental illness such as psychopathy, a human will feel guilt and shame and may even feel the need to turn themselves in for what they’ve done. People may act selfish enough to not say anything, but it will stick with them as the human conscience is extremely powerful. Even if nobody finds out, karma will work its magic.
