There does not appear to be any intent on your part to deprive the store of the money for the candy. You could either go back to the store and pay for the item or leave it alone and try to be more aware of the items you have when you check out next time.
Carl Spector, Esq.
Note: For informational purposes only.
From the information you provide I do not think you have a criminal law question. No one saw it happen, no cops involved and the store did not realize the error. Sounds like something your religious leader should field. You can enjoy the situation or go back and explain the error and pay for the candy. My guess is that the store personnel will fall over but that may be the right thing to do. I doubt the store will fault you in any way. Good Luck.
This appears to be a moral question, not a legal one. If your conduct was accidental, then you didn't act with the requisite state of mind to commit the criminal act of theft. Once you realized your error, however, you became aware that you were in possession of someone else's property, a less serious, but an offense nonetheless. But if no one knows it happened, then you probably don't have a legal problem, just a pesky moral dilemma. Personally, I would do the right thing and go back the next day and pay for it.
Legal disclaimer: In accordance with the Avvo community guidelines, this communication does not constitute "legal advice", nor does it form an attorney-client relationship.