Most likely is passes through the walls of the hoses or whatever just like air leaks out of a party balloon. The same thing would happen if you turned the natural gas off at your lake cottage and tried to fire it up 4 months later. Don't lose any sleep at all over this matter.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.