If you were using the s-video input, you would have had the OSD, but if you had switched to the coax then you would have lost the OSD. Since you OSD went away, I assumed that the plasma got switched to the coax input.

We're all confused why miscanthus can't get OSD via s-video, but it's a very isolated and currently unexplained situation and since you had the OSD working already I can't imagine you running into the same thing.