Does anyone know of instances where you were caught shoplifting in a grocery chainstore by their in house loss prevention officer and the police are called, but the police did not end up laying down charges for theft?

Did the loss prevention officer have influence over the possibility of having charges laid?

Yes, they can have influence over whether charges are laid or not.

If you were lucky enough not to have charges pressed, then you are indeed lucky.

Some stores have a set limit you must exceed for them to press charges, the major chain store I worked for did.
What they do sometimes is make you agree not to go into the store again on paper and also take a pic of you so employees can spot you if you do enter.

Follow up question. If the police did lay charges and set a court date, is there any way to have the charges dismissed? For example, talk to the staff at the store?

I don't understand as to whether the charge the police laid (theft under $5000) is filed against me by the store, or if it's filed against me by the government.

In a criminal case, the state is the prosecutor. Only in civil cases is a person (or company) the plaintiff. Theft is a criminal offense.

However, if the store declines to prosecute, the state will usually drop the case.