If you haven't submitted a support ticket, that would be the first thing to do. You'd probably also want to screenshot the activity (to show your Plat purchase) on your Steam account and attach it to the ticket.
Like the others, I've also been affected by the Lanka's mysterious and abrupt disappearance. In my case, I lost the blueprint and it's not showing up in the dojo lab or on the clan research list anymore.
See Makotori's post: Lanka missing?