First, stop panicking. No you won't weigh a stone heavier in the morning. You might well have stalled your weight loss a tiny bit but it won't be the end of the world.
Atkins bars don't have many fans on here - neither the indulge or the regular kind - as they are evil stallers and are a new addition that dr Atkins himself would have been against.
Basically the Atkins bars (both the ones allowed on induction and the others) are sweetened with sugar alcohols. These won't take you out of ketosis but - like normal alcohol - they are a fuel that your body finds easier to burn than fat and as such will burn first. What that means is that your body has to burn off the sugar alcohol in the bars before you burn more fat.
The Atkins website says you can have up to 2 Atkins products per day. I can't imagine anyone doing this and losing weight - and there have been a couple of people posting here in the last couple of weeks alone upset about not losing who were eating regular Atkins bars.
Dr Atkins created a diet to help people lose weight. He was wary of artificial sweeteners in general and he would never ever have advised people to eat sugar alcohols.
Atkins nutritionals is a company with license to the Atkins name. All versions of the books and website since Atkins death are through them. They want you to stay on the diet as long as possible while paying list of money for their overpriced 'fake carb' products like the bars.
All in all, Atkins bars are preferable to eating actual sugar, when you're desperate and might fall off the wagon otherwise. Eating them regularly unless you're incredibly lucky may well cause a stall or even slight gain.
One bar - even the bars not meant for induction - isn't going to break your diet, just keep going as you were, you'll still lose. But I'd stay off them in future while you're still trying to lose unless it's an emergency.
