Have you ever entered Classic or TBC Classic after the TBC launch? By that, you chose an expansion for your character. If you didn’t, it should now be on TBC Classic.
I am not sure about that, because
I think, you might see the (not activated) clone on Era. There are free transfers on Era servers to other Era servers. Or can you actually enter the world with your character on Era? In that casey you won’t be able to play TBC with it, like Dottie explained.
Or were you possibly on one of the servers that were recently shut down in TBC? Then you should be able to find your character on another TBC server at some point.