How to help a friend who lives with their abusive parents

I have a friend who is an adult with mental issues and lives with their abusive parents. They are afraid to do anything and in the past when they tried to stand up for themselves it never end well. It even gotten to the point where the police got involved but took the parents side because of their mental illness. It has been almost a year since we last talked and the first thing I heard from them is that their home life has gotten so bad that they ran away without telling anyone so they could get help from the hospital for their suicidal thoughts and now I am afraid what would happen once their parents go get them since the police had to get involved since this is considered a missing person case. What should I do.