I have been in this situation with my husband's father. The first step is to find people in his area who know him and ask them how he's doing. You'd be surprised what a post to former neighbors on Facebook can do. Ask other family members, old friends, church friends, and even old coworkers. Mention that you don't want anything, that you only want to know if your parent is okay. In the meantime, consider seeking a spiritual or social self-help group that specializes in family estrangement. Things may break down or your reconnection may never materialize. Support groups really do help with that.

Once you have communicated, stay neutral and very vanilla. Don't ask much. Don't talk about anything personal. Try not to bring up the past, even if feeling nostalgic. Dry conversation is probably the best bet for the first year. How is work? How is so and so? Watched any good movies lately? I know it will be very hard to deal with due to the fact that you likely desire more, but it has to be tiny baby steps. You will also likely have massive setbacks at first if there is hostility involved. Realize that if that happens, just take a break and then start back up with the plain relationship again.