Hi, I'd like to help you with your question.
It sounds like your daughter might be in an abusive relationship. The constant moving, cutting off close family and your daughter's reaction when seeing you all could be attributed to abuse. Also, the man she is with shows little interest in meeting you and establishing a relationship. He also does not reach out for help concerning your daughter's lack of contact with you or others in her life. That says that this may not be of her doing but his. He does not want her to be with others and have relationships she can use to help her out of the situation.
Since your daughter is an adult, there is not much you can do to control her behavior. But you can try to help her by learning what you can about domestic abuse. If what you learn does sound like what you are seeing with your daughter, you can try to suggest it to her next time you are able to see her. You can also provide phone numbers and on line sites that she can use to help herself, when she is ready.
Here are some links and other resources to help you:
http://www.thehotline.org/- give her this site and the phone number and suggest she call anytime she needs to
Why Does He Do That?: Inside the Minds of Angry and Controlling Men by Lundy Bancroft
Finding Your Way Through Domestic Abuse: A Guide to Physical, Emotional, And Spiritual Healing by Connie Fourre
No Visible Wounds: Identifying Non-Physical Abuse of Women by Their Men by Mary ***** *****
If you can find her again, see if you can provide her with the above information. Tell her to call you anytime she needs help. She can seek help from the police, hotline and shelters if she needs to. And they will keep her safe. She just has to want to get help for this to work. Convincing her of that will be hard since her boyfriend has had control over her for a while now, but all it takes is a small desire on her part to want to leave to change the whole situation.
You can also contact the local authorities to find out what you can do to get her out of there. They may not be able to help much, but they could keep an eye out for her, especially if the neighbors are willing to call if they see anything.
Let me know if I can help any further,