It was all so spontaneous and rushed on DS, that I'm guessing Thayer just happened to be there.
I lost track completely back then I think. They stopped telling us in voiceovers that it was PT, and I don't think they cared. They'd ditched "RT" and the "present" for the romantic world of 1840/1, as depicted in so many of those novels by female authors, intending to stay there, I guess. It actually helped them, they probably thought, to let viewers forget about RT vs. PT and all that. This romantic past setting was even going to have its own "Barnabas", a vampire that is, going by the last episode, so they had everything they thought they wanted, and gave up nothing.
They were rectifying the supposed (ratings?) mistake of leaving 1897, I guess. Only, 1897 did so well because of writing and not just atmosphere and romanticism. And 1897 was darkly, disturbingly "romantic", very different from the straight-ahead romance of the 1840s.