It's been a long time since I watched Bleach, but what ever happened to Rukia? Is it true that she vanished or something like that?
The last time she appeared was at manga chapter 604 - REVITALIZE (until now).
As the manga is still ongoing (currently it is at chapter 608), she will keep on appearing at the following chapters.
You heard she vanished because of the final episode of Fake Karakura Town arc: episode 342 "Thank You". Where Ichigo loses his shinigami's power, so he lost the ability to see her in shinigami form, so she "vanishes" from Ichigo's sight.
From this wiki, this is the moment where she "vanish":
As it becomes harder for Ichigo to see her, Rukia knows this is farewell. Mocking Ichigo's sad face, she states she will still be able to see him, much to his displeasure. Rukia, disappearing from Ichigo's sight completely, leaves through a Senkaimon as Ichigo, bidding farewell, thanks her.