Just looked at my reservation in August for SEA-IAH-IND. The SEA-IAH is the overnight segment and I had 10C booked. However, my seat in 10C no longer existed and became a "-" so I changed it to 27A.. What's the reason to this? I understand I'm not an elite on CO but why was I given the seat in the first place?

What are my upgrade chances for this overnight segment? I don't expect too many people flying it... well I hope not...