In Virginia, yes, an attorney may maintain representation of a fugitive client and must not disclose where the client is. In other states, the rules can be different. Some places you have to say, some places you have to stop representation. It's a balance between client confidentiality and attorney obligations to the functions of the judicial process (allowing your client to be a fleeing felon). In other states, there is more leverage for the attorney to be able to get the client to turn themselves in. Obviously JM does not have much interest in the attorney's advice, which has to have been to lay low and would be to turn himself in.
My guess of what brought about the newer charges -- pubic hairs matching HG in the trunk. That would support those charges without her person being found. Wearing pants, not likely transferred by a hug. No knowledge, just a guess.
The nursing student lady needs to call the tipline for this. If he had a practice of making such offers, perhaps someone took him up and perhaps (given that he had roommates) would know what back country lane he liked for romance. And that would be a likely dump spot. If this is a "something gone wrong" scenario, the dump spot is someplace that would pop into his mind quickly and that he knows. If it were someplace he googled with his computer, LE would be there already. So anything anyone knows about rural places that he has hung out at has helpful information.