The somethingâs wrong voice
I've just realised how similar these two little scenes are.
This, literally the first words Aziraphale says to Crowley:
-Hello, it's me. Don't say anything. Are you there?
-Should I say something now?
-No. Meet me over the road from the bookshop.
and this, from their last conversation:
-What's that lovely human expression? Oh, yes. Hold that thought!
And we all remember how the first scene was immediately followed by this acknowledgement:
So, if Crowley knew something was wrong from Aziraphale's voice over the phone right in the middle of their precious, peaceful, fragile existence, wouldn't it be more than obvious to him in the final 15, right before their devastating exchange started. The difference being, of course, that this time Aziraphale literally couldn't tell him: he almost immediately started to stutter. It continues like this:
-I have some incredibly good news to give you.
-Really?
-I, um... So, uh, um.. The Metatron! <there is a pause and he continues>
And this 'Really?' is almost 'You're really trying to convince me it's good with your Something's Wrong voice?'. Which makes me certain that Crowley knew Aziraphale was in trouble and didn't believe Aziraphale was sincere about any of the 'Heaven is good' stuff. Which also doesn't mean that he agreed with his choice, of course.
What's important for me here is a clever and thoughtful Crowley, not just a heartbroken Crowley. Look at him right there, listening and watching Aziraphale with such attention:
I don't believe he missed any hints. I'm sure he'll put 2 and 2 together pretty quickly. This actually makes two clever supernatural beings working on a PLAN in s3. The only problem is they aren't talking.