I've seen various comments about how "uncaring" Aziraphale behaved towards Crowley in the bar while he's discorporated. My goodness, WE could certainly see Crowley's pain.
**But could Aziraphale actually SEE Crowley at this point?**
I'm feeling pretty sure that he could NOT. Aziraphale never makes eye contact with Crowley during this scene - he could only hear him.
When Azi heard Crowley say that he "lost my best friend", he didn't know yet what Crowley had witnessed - that the bookshop was gone - and that he thought Aziraphale had been killed. The last thing Aziraphale had heard from Crowley was that he was with "an old friend" and couldn't talk.
Did Aziraphale know that Crowley was referring to him as his "best friend"? Not sure but I hope so - there was a significant pause before he responded so he certainly seemed to process the statement. Had it ever been said out loud before? Perhaps not - so it could have caught him off guard.
Look, they both had A LOT going on in their heads during this scene - plus I don't know (or want to know) what it's like to be "discorporated". And let's not forget the fact that the WORLD WAS ENDING very soon. So I'm giving him a break here.
Here's what Aziraphale did know: he needed to get back to Earth - and to Crowley - to help prevent Armageddon. Because only together would they be able to save the world they both loved so much.
And they did.
BONUS: I hope they eventually had a discussion about what happened that day. I doubt it, but I can dream, can't I?