The discovery sounds like a hoax. When UCLA film preservastion expert Janet Bergstrom (or at least, an online version of herself) offered her expertise in identifying the found reels, the guy kind of just disappeared. Hopefully it isn't just a prank, but it most likely is.
Given that, I don't necessarily find it troubling that 4 Devils will never see the light of day. At least we have other Murnau films to help us visualize what 4 Devils could have been. But in terms of our cinema, we will never know the feeling of watching silent versions of ourselves, nor how masters such as Conde and de Leon depicted Filipinos during their peak. I don't think you can ask "what are some of our lost masterpieces." Simply, that our cinema as a whole is a lost one, both in being unseen and in being absent from the larger discourse on/about cinema.
And I think it is disappearing as we speak. I argue that we are already losing our current crop of films even though some of the best of the lot have only been made as late as a few months ago. Films are not being reproduced (to DVD or video) at a larger (or large-enough) scale, and film screenings are typically limited in duration and accesibility. From the pito-pito films to the digital creations that now represent much of the present Philippine cinema, films are made, shown once or twice, then shelved never to be heard from again. Sure, nowadays the filmmakers, aided by the new technologies available to them, are probably savvy enough to back up their own work for future reference (really, based on my experience using a telecine or burning a DVD is like hitting CTRL+S). But as long as their films are seen by a few, we might as well consider them lost.