Perhaps we're viewing the role of alley man incorrectly. What if alley man was there to try and warn Claudia of a threat or some danger?
My trail.of thought is :
Person A is closely connected to Claudia and the person(s) who wanted to harm her. Person A hear"s about plans to harm Claudia, but as they are well known, cannot be seen anywhere in the vicinity of CL's home.
Person A asks a trusted friend/family member, Person B, who is not known to any of the above and not from the area, to warn CL.
Person A tells Person B how they can access the rear of the property via the alleyway.
Person B, not knowing the area goes back twice, as they aren't sure they've got the correct property (possibly calling Person A to confirm they are in the correct place).
Person B doesn't get any answer from CL, advises Person A, who asks that they wait around to speak to her
Person B waits all night (probably in a car near to the property) and tries again in the morning (in case Person B believes they may have missed her returning home).
Neither of them would come forward. CL is already missing and whatever fate she had would be them (or their families), if they went to the police.
Like I say, it's just a thought.