Yeah they don’t count in real money, they count in “FS2020 credits” hehe… Maybe what you see is a forced de-installation because the scenery does not work anymore. I recently lost a payed scenery too: London, made by Orbx. I deleted it manually via Content Manager. It did not work properly with the GB London update. Now it shows “NOT INSTALLED” but… it is still available for download :
… so maybe you need to check ? You’ll see the list in Profile - Content Manager, your missing airport could be deactivated, standby for updates…