Trip_Id from Vehicle Position API call is missing in the corresponding GTFS


Dear all,

I am trying to match between the real time data transmitted by the buses and the GTFS.
For this, I was parsing the received data and have noticed that a Trip_Id (433201) that I received on 19-October from Vehicle Position API was missing in the corresponding real-time GTFS.
What can be the reason and what should I do in this case ?

Thank you in advance,