After a lot of research and ground work, I'm happy to finally be able to report that we have some good news. We succeeded in making contact with a family member who reports that Harry is OK but wasn't willing to provide any additional information about his absence at this time. Of course, we respect Harry's privacy and don't need any details or explanation, just knowing that he's OK is what I wanted to hear and I'm sure you all feel the same although we certainly do miss him around here.
We also asked this family member to pass our best wishes to Harry and to let him know that he is in our thoughts. Hopefully, they will do so and it will prompt Harry to come back soon.