I recently started training at my old dojo again after an 8 year absence. I was 1st kyu then and was a few months away from Shodan when I had to quit (personal).
So when I got back to the dojo I had a white belt on. Three reasons. I didn't want to assume that I was an automatic black even though it's back to the same school. Two, I wanted to come back with a beginner's mind. Three and most importantly, I can't find my black belt!
First few training sessions were fun. With my CI's permission I joined the beginners. Only 3 people knew me previously, my CI, Assistant CI and one senior instructor (he was actually my junior!). The beginner's class had already started when I joined so there were a few who thought they could teach me a thing or two. Some were nice but there was one or two who would actually teach me the wrong things!
There were also some "seniors" who'd help me/us, most of them are great but there's always the odd one who thinks his brown or black belt means a lot. I didn't assume that they can't teach me anything, I'm always open. I have after all been away for a long time and was a little rusty.
After a few sessions/weeks, my CI told me to join the advanced class (although I was still practising with the junior grades to get myself back to speed) and that was when many realise that I wasn't who they think I was. It was a nice feeling but I wasn't there to show off so I didn't rub it in, just went along with my training.
Finally found my black belt and now wearing it!