Ronster said:

There is nothing that suggests he does not detect them considering the first in cockpit shot we see is Han having a Radio conversation with one of the cloud car pilots I'd say he has detected them alright.

This is another example of a scene starting in the middle of a conversation that started offscreen, which somehow always makes the talk seem more "real" to me, though I wouldn't know how to explain why.

That was why my only beef with ANH:R was the rearrangement of the Obi Wan hut scene, as putting it in the original script form made it feel more staged and expositional than it felt in the official edit. But that's off topic. The cloud car chat has no other way to be edited. So yeah, no possible way to make it seem that the Falcon was unable to detect the cloud car.