My question involves criminal law for the state of: California

I stole some item under $15 in Walmart in 2001 when I was 15 or 16 years old. No police, no court, no picture taken. I was sent home and paid the fine of about $150 that came along from a mail label "WalMart". I am very unsure if that affect my record/background, and I do understand that it'd be sealed if it had been file. I am now 23 years old and thinking of applying for Naturalization and is very concern about this past.

So my question is if I file for Naturalization now, do I have to confessed this ? Since no cops, no court and no picture were taken, does that affect my backgrounds or am I still clean from the eye of FBI ?

Any help is appreciated.