I already heard back from TST! Unfortunately I wasn't all that happy with what they said.
TSTs reply was as follows:
If a sensor is lost it will read the last temperature and psi for that position. If the display does not receive any data from a sensor, and no parameter has been violated the display is thrown into stasis and it holds on to the last data received as it continues on with the rotation to the other tire positions. It may take several minutes before it recognizes that the sensor is not present.
Someone above just posted that it can take an hour and not minutes to notify of a lost sensor.