Help! Air tag found moving with me

Hi. I recently received a notification while driving that an unknown airtag is found moving with me. I looked at the map and it started picking up the signal after I exited the highway and stopped few blocks away from my home (recorded about 9 km or my route). When I got home, I tried clicking the “Play Sound” option several time but it always gave me a message that the air tag is no longer reachable. Could it be that my iphone just picked up a signal from a nearby car driving the same route as me? I searched different nooks and crevices my car and couldn’t find any airtag. Should I be worried? Or could it just be a false alarm? I read it should emit a sound after three days. Will it still emit sound even if the owner has disconnected it from its account?