The files owned by a Google Service Account were trashed and permanently deleted from the trash by my normal user account; Service Account storage space was not reclaimed as expected. Existing files owned by the Service Account adds up to 4.56 GB (4557015060 bytes), the about Google Drive API response says the Service Account usage is 16.08 GB (16084076368 bytes). The difference is 11.52 GB — what I should have gotten back.

I tried using the API to get a list of deleted files but they do not show up at all for either the normal user nor for the Google Service Account. I tried uploading then deleting a tiny file using the Google Service Account in the hopes that it could recalculate the storage space but that had little effect. The files were permanently deleted over 2 weeks ago. What am I missing?