Must be a medical show thing.. I never checked in or out with anyone outside when on booth duty. I can't imagine what that would look like at McCormick Place or Jacob Javitz. There's usually a place where you have to go to hire union thugs (Electricians, Carpenters, Teamsters for carting stuff around other guys for doing complicated stuff that includes screwdrivers or other tools, and a place for exhibitors to pick up credentials and such like.
Eg.
In San Francisco, for example, both the International Alliance of Theatrical Stage Employees (IATSE) Local 16 and the Sign Display & Allied Crafts Local Union 510 claim jurisdiction on hanging plasma monitors. To avoid an argument on the show floor, my answer was to hire a laborer who carried cards for both unions.
Sure, or just try to arrange something when folks from a trade show are in town. They may include your meeting in their report to management.
Best regards, Spehro Pefhany