Cas shook his head as he began to gather anything dry enough to burn. "We do," he replied. "There are various humans who are important to God's plan. It's entirely possible that you are important. Simply not within my reality. Each parallel reality is different. So much in fact that the people hailing from them are not the same people. Merely echoes that vaguely resemble one another."
After all, he'd met another Castiel. He'd been...weak. Not by choice, but rather it was a learned helplessness that Cas himself had done his best to remedy. They shared few interests. And preferences. The only things they'd had in common were a past, a name, and a vessel. Nothing more.
"I would prove my former status to you if I could," he replied heavily. "But as I am now, the most I can do is give very vague readings. My senses have yet to dull to the point where I cannot see as an angel does."