2 of my giveaways mysterious disappeard?

probbaly reported as fake..

were they keys?

probably you wanted to gift keys from the bundle which are not allowed, even if you somehow managed to do before

Its better to ask support via ticket than asking here.

I've ninja'ed your games before you gave them away!

Well, people already gave you the answers - probably they were considered as fakes and reported (and taken down by adminstration) or they were violating the site's rules (keys for games from some bundle). If the second eventuality is correct, then you can still give away those keys here on forum, just not by making a giveaway.

Did you make Really Big Sky giveaway?