We must check with that scenery, it's likely they used (probably in a recent update, since nobody ever reported it so far) a scenery handling similar to our own, outside of the .bgl format. Of course, our sceneries are recognized by GSX, so our buildings are not removed, but sceneries from other developers should be explicitly supported.
The reason for this is that when you select a parking in GSX, default ground vehicles must be removed from it, and it's exactly the same problem that caused AES+FSUIPC to remove GSX objects when a parking was selected, so FSUIPC had to be updated to recognize FSDT objects, we'll have to find a way to recognize the Aerosoft objects and not remove them when the parking is selected.
