I am not sure why it matters so much that he was driving on a suspended license. A probation officer doesn't even technically need a search warrant. It would be very easy for the police to search this man top, bottom, and back again.
I think the police would have needed a warrant. Though some, or perhaps many people on parole from prision are required to sign "Fourth Amendment Waivers" allowing the police to search their homes with out warrants and to stop and search their cars and persons "just because", RL is on probation, not parole.
My impression is that the types of parolees with signed waivers are usually known drug sellers with multiple arrests and convictions or perhaps true public safety hazards ( multiple arrests for assault, theft, drug use etc). Even with his two DWIs and restraining order, I don't think the police would have considered RL to be a true public safety hazard. .