Having had this experience, depending on the relationship you once had, this meeting can be either awkward or you can pick up where you left off without any trouble. The woman I met after such a long time had been a card playing friend whom I enjoyed as a person. She was funny, kind, and willing to answer questions about kids as she was a nurse. We lost touch when I quit playing cards, once I moved to a full time teaching job. She also went from part-time to full-time.
When I accidentally ran into her at a store, I was quite pleased to see her. We shared stories of our kids, stories of our work lives and stories of our husbands. Shortly thereafter, she told me that her husband had cancer. I supported her emotionally for several months to help her through this awful experience. I felt glad to do this as I had lost two sisters to cancer. It was hard to do as she and I had missed twenty years of each other's lives, but the effort worked as it was a shared experience.
I was glad to do it, she was glad to have me, but after he died, she again disappeared out of my life. I still have no idea why, but it is what it is. I still feel sad that she won't answer calls or email, but she is entitled to do as she wishes. I still think of her, but have learned to leave her alone as that is her choice. This is how I felt when meeting a friend after twenty years. My own experience helps shed light on why Jimmy, a policeman, was reluctant to acknowledge Bob, a wanted criminal, and be the one to arrest him after a distanced twenty-year friendship.