There's no way that 2 spoons of weetabix will have harmed your weightloss hon, even putting ketosis aside, you've still had a huge calorie deficit this week which would result in a weightloss anyway.
Carry on the rest of the day as normal and forget all about it. Old habits die hard and it's a lesson you've learned, next time you'll be more careful about not eating while feeding your wee one.
Don't beat yourself up over it either, it's a simple mistake, we all make them, and you have done fantastically well on LT, losing lots of weight. Just keep in mind how far you've come and why you're doing this. Why not treat yourself to a nice pampering session, or a new item of clothing, something, anything, to reward yourself for the hard work achieved so far and put the weetabix down to experience.