The VSS on the Taurus is a variable reluctance Hall Effect sensor. It is driven off the final drive of the transmission. As with all solid state devices, they can become intermittant. Heat and vibration can make them work again.
If you had a way to patch into the circuitry you might be able to see if the sensor is working i.e. producing a variable frequency voltage. The sensor has to have power and a front wheel has to be turning. If you see the voltage at the sensor, check again at the PCM
The quickest way is to just replace the VSS. It is accessible from outside the transmission. The Alldata part cost is $62.78 and labor is 2.7 hours?. I have no estimate on the diagnostic time.
Hope this helps.