If we read PC 25850, section (b) carefully, it says:
(b) In order to determine whether or not a firearm is loaded for the purpose of enforcing this section, peace officers are authorized to examine any firearm
carried by anyone on the person
in a vehicle while in any public place
on any public street in an incorporated city
prohibited area of an unincorporated territory.
Refusal to allow a peace officer to inspect a firearm pursuant to this section constitutes probable cause for arrest for violation of this section.
To me, OP was in neither of the bolded areas.
If the firearms are in cases, it is not "on the person"
. He is clearly not "in a vehicle"
, nor was he "on any public street"
or "prohibited area"
. To me, a prohibited area
would be school zones, federal buildings, etc. To say that the lobby of a gun range is a prohibited area is stretching, even though one would not want a customer discharging weapons there.