Where the hell are you?
When Cas called Dean in 11x01, the first thing Dean said was: “Where the hell are you, Cas?” Let’s think for a moment. The last time Dean and Cas saw each other, Dean beat him up and told him to stay away from him (10x22). They haven’t talked to each other since then. Are we to believe that between getting rid of the Mark and receiving Cas’ call, Dean didn’t try to communicate with Cas?
I’m calling bullshit! My headcanon is that once they were on the road, Dean called Cas a couple of times. He didn’t get any answer from Cas and that’s why when Cas called, Dean immediately asked about his whereabouts. Besides, if you can rewatch the scene, you will notice that when Dean’s phone rings, he looks desperate to pick up as if he’s been waiting for someone to call.
In 10x14, Dean had been trying to contact Cas, but Castiel wasn’t answering. When Cas finally called him back, Dean’s first question was: “Where are ya?” I checked all of their phone conversations in seasons 9 and 10, and I noticed that when Cas is the one calling, Dean has other things to say when he answers the phone as long as he hasn’t been desperately trying to contact Cas.
When Dean asked Cas about his whereabouts in 10x14, Cas’ immediate answer was “Illinois”. But in 11x01, his immediate answer was “I’m OK.” Dean wasn’t asking that, but I’m sure he had probably sent a “How are you?” text to Cas when he noticed Cas wasn’t answering. Why do I say that? Because when Cas doesn’t answer the phone, Dean freaks out and uses plan B: texting.
In case we’ve forgotten that, here you have a picture of Cas’ phone in 9x18.
We can see the 6 missed phone calls from Dean and the icon that indicates Cas has god-knows-how-many text messages from Dean. Cas hadn’t called or texted Dean back and Dean was, naturally, freaking out. I’m sure the same was happening to Dean in 11x01.
Just to end this post, I’d like you to watch these two videos and compare Dean’s desperate cry of “Cas!” in both scenes. Last time Dean sounded like that, Cas was dead. No wonder why he wants to go save Cas asap.