Good info on resources. I also prefer printed maps, and my truck is a roving map library (mostly Auto Club of So Cal county scale, which are no longer produced, you can guess what my opinion is on that).
Dispersed campsites by definition won't show up on maps, but you'd have to know the policy for that particular landholder, as was pointed out.
But when on the ground, look for existing fire rings, of which I've seen many from dirt roads in the desert. BLM (and probably other agencies) allow camping at 'established' sites, whether or not marked. They tell me they accept the presence of a fire ring as an 'established' site, so you can camp there without problem (or with a good explanation if a ranger does stop by and question). BLM HQ in Barstow has an internal database similar to GoogleEarth showing all such sites they've identified, and there are a bunch of them in the East Mojave whatever-it-is.
Obviously, whether a ground fire is allowed at that location at that time is another question.