OP
I ran into a similar question when i first bought the falcon collection as highlighted by Flow32 above. Although the download location is not completely obvious, it is absolutely there. From your account / games, You can click on the falcon gold collection, view downloads, and list the entire set. Falcon 4 is near the bottom.
Also - GOG support are actually responsive and will contact you if you ask them for help. They responded to me in the time i worked it out.