I think it's just 'off limits' in BW times according to canon, with it's location kept secret. But I blew it up in Vernoverse. No more fleshlings ruining TF stories!

As for Spark, yeah, if a Prime controls the Matrix, who is an Autobot, how can new Decepticons come online?! It needs a definitive answer once and for all! Not some conglomeration of every different continuities theory smudged together and passed off as a working model.