Certainly, if this was crystal-clearly intentional sabotage, your brother and SIL are pretty messed up. But I agree with the earlier message that it is hugely possible that since they aren't on the diet, they probably have pretty limited knowledge of the details. I think a lot of people just know of it as "lots of meat, bacon, etc and no veggies or potatoes or bread". Few people really know the specifics of carbohydrate counts unless they are following the diet. So keeping an open mind about their motives, and then letting it go even if you truly believe they knew the honey would sabotage you, sounds like good advice for a happier you. But I would consider brown-bagging it next time...

PS I agree though that this amount won't harm you, and your continued weight-loss should be fun to show off!