Steamgifts thinks I own a game I don't

Free weekends tend to do this. Just wait out a few days.

i don't like this too, since i've never played a game on free weekend, but those games still somehow appears on my games' list :(

More than a few days. Can often take a couple of weeks to clear from your steam account

One of my friends still can't enter Sanctum giveaways, despite force syncing at least 10 times in the last three days :3

it's cause of the free weekend of payday, once it's gone from your library re-sync your account

same for me just wait it out, could be hours, could be weeks

I just synced for a third time and it worked. So I guess the moral of the story is, keep trying to force a re-sync until it works.