What is the exact orbx bgl that contains the closed T hangar that you reference? Is it part of a specific airport? Does that specific airport contain a closed T hangar?
First open ADE
Go to Open Airport by BGL .Drill down until you find the Scenery Folder and look for a file with airport designation + something like ADX or APX. Ignore any with CVX.
Once you have the AFCAD (ADX or APX) loaded, look for a .bgl file that says Library. Chances are that will contain your hangars unless there is one that actually says "Hangars" in the title. It varies as to the complexity of the airport.
Go to Tools>Library Object Manager>Add File and add that .bgl to Library Object Manager.
Now you have all the objects in your ADE library, but no thumbnails. Open ModelConverterX and import the file you just added to ADE Library Object Manager. You should see pix of all the objects. Use the Capture New Thumbnail feature of the LOM to add the images. Tedious but necessary. Remember not to use any Orbx objects in any airport creation that you may distribute to other people.