Wearing the black hat; you're gone!
C'nut, it doesn't matter which way the mirror is bent, it's an interesting analysis, but the fact remains
OP has changed lanes without due caution.
A lot of opinions offered from a few lines of description, but IF it were necessary for you to get back to the RH lane, you should have been indicating right as you were passing the turning traffic, giving you the legal requirements (30m? 3sec??) to change lanes, and no-one could've come up along-side you.
Why people make things difficult for themselves, I'll never know!