Assuming it has cleared from your Steam account (which doesn't always happen right away), then you need to re-sync your account here so it sees that it is gone. If there is a bug it is on Steam's end. When a game goes on a free weekend you essentially 'own' that game for that period of time (it will appear in your list of licenses), and if your account here is synced during that window then that is last data that it saw. Solution: re-sync here. If you Steam profile is public I believe it will auto-sync once a week, so try to arrange it so that it does not happen during any free game time. Tuesdays and Wednesdays are generally the 'safest'.

Sync steam account and save changes. Works for me.