A lesson I learnt came from a fitness guy I watched. He said, missing out one day happens. Shit happens. Missing out 2 days is a choice.
I couldn't go out yesterday cause a storm came through. So I did 2 times what I normally do. I don't know if the effects will pan out, but at least I can say I did not slouch. I am ~3lbs away from my desired weight.
More muscles will consume more kcal. You could lose the 1.5kg simply by eating at maintenance and working out over a few months.