Are you sure the top tube wasn't already cracked? If you didn't even go down it sounds like a very suspect crack. I've binned numerous carbon bits quite hard and not as yet had an issue like this.
Ultralight frame? Manufacturing fault? Was it ever dropped onto an edge? It just doesn't sound like the kind of crash that could break a top tube unless there was already something wrong.
Are you sure the top tube wasn't already cracked? If you didn't even go down it sounds like a very suspect crack. I've binned numerous carbon bits quite hard and not as yet had an issue like this.
Ultralight frame? Manufacturing fault? Was it ever dropped onto an edge? It just doesn't sound like the kind of crash that could break a top tube unless there was already something wrong.