I just had my first solo 2 days ago. Still smiling!
The debrief involved my instructor asking me how it went, what I thought was good, where i could have done better. Can he give you a real de-brief when he hasn't been in the plane?
I was more than happy to talk it through (at a hundred miles an hour yes) and im sure most first solos feel the same.
I don't think the student would take that much in straight after first solo to be honest - i for one was still pleased i came back in one piece, with the aircraft intact and nose wheel safe and sound. I was quite happy for the instructor to listen rather than lecturing me on how I flew for the first time alone.
Don't think lack of interest should even be mentioned - if i thought for one second i was paying hard-earned cash only for my instructor to be half interested, i wouldn't be at solo stage - and if i was it would be with another instructor!
Cheers