This may sound bizarre but it could have been a case of you reeling in, and at the same time the carp took the bait in, thus you having a carp on!
It can happen though that the carp can be hooked, then move off left or right and not register on your alarms. It's one of them though mate, I guess you'll never really know what happened. Generally though, as the name suggests, the 'Bolt' rig is designed to make the fish bolt on feeling the resistance of the lead. But, until the fish do feel the resistance, there's every chance the fish could have been sitting there, sucking and blowing trying to eject the hook, but thats another discussion........
