In Fallout: New Vegas, you can complete a side quest called the Aba Daba Honeymoon. This quest is located in the Red Rock Canyon and involves talking to two people. Jack, the first, will speak in a slow burnout cadence. Diane, the second, will speak in a different style. You will find out that Anders is not back when you speak to Diane. You will then have to find him to complete the quest.
Fallout: New Vegas – Aba Daba Honeymoon