User blog comment:RemosPendragon/Space Marines policy/@comment-33731050-20150916235531

I don't see anything wrong with fannon Thunder Warriors surviving the cull/scouring, but seeming how difficult it is for Thunder Warriors to maintain themselves I think there would have to be a very good reason for them to be alive. Of the two who known to survived the cull, one died of "old age" not long after, and the other only survived because he was an incredibly influential crime boss who was able to steal Astartes Gene-Seed.

Loyalist Traitors seem to be a big no for me since it is cannon they all the known survivors were rounded up and sent to Terra to serve the Sigilite, and so are really all accounted for already. And though there may have been others, I doubt that they would have lasted very long at all, having no support from either the loyalists or the traitors. But I guess we can never know.

But that is 30K era. In 40k I don't think loyal traitor defendants are cannon friendly at all, or at least chapters that are known to be descendant from traitors. Cannon has a few that are thought to be, but usually when people write them in fannon they tend to just be recoloured traitor legions.