as i drove home from grocery store, car would periodically bong three times - no message came on to the display. what was it trying to tell me?

What is your question?

I had placed several bags of groceries on the passenger seat. Could it be that it detected enough weight that it thought there was a passenger who needed to be belted?

What makes this problem better or worse?

it only happened this once

How long has your 2012 Buick LaCrosse had this problem?

one time thing