If you detach yourself emotionally from the issue and think about it, this is the behavior you would want: If you were a thief trying to rebuild a machine to gain access to its encrypted files, you wouldn't be able to. This is what's happening to you now. Sorry.
If you hadn't rebuilt your machine, this article on recovering encrypted data files would help you with your lost key problem, but now that you've formatted the disk and lost any recovery agent that had been configured, it doesn't apply in your situation. I include it here in case future readers encounter this problem.
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