The statue of limitations governs the time within which the DA must file charges, not the time that the police officer must prepare the report. A police report is generally prepared and filed with the DA within days of the crime occurring. After receiving the report, the DA will look it over and decide what, if anything, to do about it.
The length of the statute of limitations depends whether you were arrested for burglary or shoplifting. Shoplifting / petty theft is usually a misdemeanor. The DA must file charges within 1 year. Commercial burglary can be filed as a misdemeanor or a felony, in which case the statute of limitations is either one year or three years.
It sounds like the offense would be considered a misdemeanor based on the way you have written your question. The Statute of Limitations for filing on misdemeanor offenses is one year in the State of California.
If the dollar amount of the alleged theft is more than $400.00, I suppose the prosecutor could charge the offense as a felony, in which case the time for filing would be three years.
If the person arrested has prior theft convictions, the case might also be charged as a felony even if the dollar amount is lower.
Start looking for a local attorney that practices in the court where the case would be heard if it is filed. With minor theft cases there are often diversion type programs to avoid having a conviction on your record.
If you are talking about shoplifting/commercial burglary, the amount chargeable as felony theft has been raised to $950, not $400. Even if the amount exceeds $950, it still could be charged as a misdemeanor in the DA's discretion. If both charges get filed as misdemeanors eventually the statute of limitations in CA is one year; if charged as felonies it is three. I doubt seriously that any police officer doing his job properly would wait the entire statutory period before giving the file to the DA. If an investigation is continuing it could be months before a final police report if filed.