Could be, but 74 years in the seed bank is a pretty long shot. Could also be that they're pretty uncommon in the park, and both I and the botanists doing transects etc have all been looking in the wrong places. I haven't quite given up hope, but I'm not holding my breath. At least they both occur elsewhere, though one of them (Pimelea curviflora) is considered threatened.
Unofficially, for a long time. Back in the late 1980s and early 1990s, when I was a member of the Biology Society at the University of Adelaide, I helped Honours Botany students doing vegetation transects. Also laid out some plates for Phytophthora surveys about the same time. But I've only been photographing the park's flora for a couple of years. Most of the work I've done as a volunteer botanical research assistant was actually in the Murray Mallee, or at Koonamore Vegetation Reserve (semi arid mallee through arid scrubland to ephemeral herb and grassland).
Wow... you must know heaps by now. I don't know too much about Eastern States plants, but I bet you've seen some interesting ones out there. I'm still only half way through my degree and hopefully I'll do honours, some small part of me believes that I can restore the urban remnants around the place (mainly because I live next to one).