Well done on your 2lb loss!
As for the Kit-Kat ... well, we're only human and the occasional slip isn't a hanging offence. In fact, from time to time it may be a good thing because it's how we DEAL with the little slips that educate us in how to change our ways. I know if I've eaten more than I know I should have in the past, I've dealt with it by ..... eating more! Crazy logic but there you are!
You had a little 'treat', you didn't make a big issue of it but have strategies in place to rectify it - done and dusted!! Well done you