Intention v. Action

Supposed you were on the way home, and saw what you thought as your jacket, oblivious with the fact that you didnt even bring your jacket at the first place. You took that jacket home with you.

Now, the intention of stealing never even entered your mind. You just innocently took what you thought it was yours.

Was it stealing, what you did? What make an act of taking something that is not yours is stealing , the intention of it, or the act of it?