It was the purple ribs that puzzled me. It has the general appearance of a Lyperanthus leaf, which is quite large, stiff and has thickened edges. I asked Cath because she has recently seen some Lyperanthus leaves emerging in a known colony.
It doesn't look like Lyperanthus to me. Its leaves are narrower, and pale on the underside with recurved margins. They also emerge from a distinctive purplish bract. I can't think what this could be. It might not be an orchid.
Interestingly, I found a large number of Thelymitra leaves when I went back to this area - none that looked quite so extreme as this one but similar... Currently following those to flowering stage so I hope to get an ID at least for those.