What happens if I go to my DMV hearing and show no probable cause?

If there was no justification for the stop, then any evidence collected as a result should be thrown out at a 1538.5 hearing. But, the rules on vehicle stops are tricky. Police can pull you over for virtually any reason. They key usually is whether they detained you for an inordinate period of time and/or whether or not the search exceeded the scope of their authority based on their reason/excuse for stopping you. You should not try to do this alone. Consult an attorney. If you truly weren't driving, the prosecutor should not be able to convict you since driving is an essential element of a DUI charge that the prosecutor must prove beyond a reasonable doubt. Again, however, the devil is in the details. So, again, you should retain an attorney to protect your rights instead of trying to handle the case yourself.

Both elements need to be proven I.e. the probable cause for the stop and that you were the driver/driving the vehicle. I suggest you get a lawyer to represent you since you may have a chance to save your license.

They return your license to you.

If you weren't driving I don't know why you have a DMV hearing.

If the DMV hearing officer finds no cause for arrest, then your DMV suspension is cancelled. No police officer is going to admit he had no cause to stop and arrest.

Without probable cause the case should go away.

If the officer who arrested you will say you didn't violate any VC, then yes you will win the hearing. But for that to happen frogs would have to fall off from the sky.