I got it too at one point. It was a class 0 planet. I was surprised when I saw it. However, after saving and reloading the game, I lost it. It sorta became a class 0 that looked like I colonized it, except I couldn't get the colony screen. It unfortunately didn't have the resource it once provided.

The description of the video event said something about improving sensors. I wonder what they'll be tied with.

This was in Beta 3 as well. I don't think it is a bug, but a partially realized feature. I have no idea however if it was an idea that was abandoned or one that hasn't been finished yet.

All I know is that Thulium is required for adding Survey module to ships... I have so far not seen a single planet that has it (although I haven't played for that long). I was in fact surprised to hear that it is a planetary resource (as such a thing wasn't even mentioned by the tutorial)... I was wandering what the hell it was, because I could not find it... I guess I just have to play a bit more, and hopefully one or two such planets turns up (hopefully some close enough to other resources too, so that I can make use of it). One survey ship to cover the whole galaxy just won't cut it! This is really clumsily done.

I just discovered Thulium. It is not a dead planet though. It looks like a planet, but has its own unique resource icon. Discovered another resource in the same system that also looks like a planet (gas giant), called Promethion. Placed a mining station between both and got access to both resources, so the issue is most likely resolved. The OP is old anyways.

  At the time the original post was made (this thread is a 4-month necro), Thulium was showing up as a single system of dead planets which could be mined but didn't do anything. It was later changed to be a standalone resource (and Prometheum added at the same time).

For some reason I find it amusing when somebody dredges up an old post that became irrelevant months ago