Then they would've first stuck their key in the deadbolt lock part above the door handle, to unlock the door first before squeezing the handle. Like I do when I don't park in my garage and hence come in this door. But they didn't.
And if they were expecting it to be their place and left unlocked, they would've squeezed the handle and pushed into the door to open it. LIke I do after just dragging my trash cans down to the front of the building. But they didn't do that either.
It was just a careful squeeze of the handle, so I only heard the slight creak of that mechanism, and didn't hear what I presume was the gentle push to see if the deadbolt had been left unlocked.
And I lied; my head is more like 18-24 inches from that door handle. But still at ear level where I sit. And if that mechanism wasn't oldish and creaky, I might not have heard it at all.
I haven't been the victim of any major crimes, just a few extremely weird incidences (like coming out to my car after work one day and finding someone trying to get into it, who claimed to mistake it for his own), so I don't consider it, but I should.