Vicissitudes of rank in Los Angeles

The show: NCIS: Los Angeles
The episode: "Keepin' It Real," first aired last night.
What happened: The crooked Marine Gunnery Sergeant Jerrold Mulhearn (Mark Rolston) attempts to switch $20 million in newly minted U. S. currency destined for shipment to Afghanistan with counterfeit money printed on paper he obtained from Agent Callen (Chris O'Donnell). The Gunny is assigned to a supply depot at Camp Pendleton. Agent Vail (Adam Jamal Craig) puts on a Marine uniform and goes to Pendleton to get Mulhearn's signature on a form, addressing him as "Sergeant." Mulhearn signs the form and gets back to barking orders at his men.
What doesn't quite add up: So Gunny Mulhearn is putting on a Drill Instructor act and he doesn't chew Agent Vail out for calling him just a Sergeant (E-5) when he's a Gunnery Sergeant (E-7)? In fact, that slip-up should've alerted Mulhearn to the fact that someone was on to him. Though I admit I didn't notice what rank insignia Agent Vail was wearing on his Marine uniform. Maybe a Marine won't complain about being called the wrong rank by a higher ranking Marine, but in the case of a Gunnery Sergeant, at the enlisted rank structure that leaves just E-8 and E-9, and someone Vail's age shouldn't attain those ranks. So if Vail was posing as a Marine officer, Mulhearn neglected to call him "sir." Hey, Bellisario: just because JAG is over doesn't mean you don't need military consultants anymore.
And another thing: I don't know how Marine SNCOICs of supply depots run their operation nowadays, but when I served as a supply clerk, I never knew of a supply chief pretending to be a Drill Instructor.