I can’t believe they weren’t issued standard sidearms. But I don’t know SOP for this kind of duty.
When I was in the Army we were issued M1911 for courier duty when transporting TOP SECRET Pershing firing tapes, a 0.38 for Airfield CQ, and an M-16 for bank guard duty. Other than that, we were not issued weapons for routine trips, in Germany, during the height of the Bader-Meinhoff terror.