Same thing here... I don't usually use the Nuendo Restoration plugins but the other day I was teaching a workshop on Nuendo plugins and to my shock those two plugins weren't popping up.
Are you on a Mac? What system? I'm on Snow Leopard (10.6), and wonder if that could be it. The uni I was teaching at had Leopard (10.5) and they where working...
I think those plugins are VST 2, which might be struggling on the new OS running 64 bit - not sure though. It might also be conflicting plugins. I also checked the content of the Nuendo app's folder and they are definitively there. I even copied them into another place, but they weren't coming up either.
If you can't find an answer here on SSD, it might be worth asking over on the www.steinberg.net forum.
Good luck, and let me know if you come right.