Could be totally uninvolved in her disappearance but presumably police officers/detectives have their prints on file for ref. how easy is it to assign yourself to a case/call as an officer/detective? surely a trail of command to trace back through......
Alleyman: if he retrieved a spare key at 7.15 was the intention to prevent Claudia from being able to get back into her house, by him or someone else sneaking her housekeys from her bag/pocket wherever she went? Did she then call someone nearby? Then ambushed wherever she went, Nag's even? Was the pocket rummaging a signal to someone, "I can't find them!"
Or in the morning or even early am, was Claudia lured to her back garden/as far as the alley then grabbed? Narrows possibilities somewhat. This is why it's important to grasp exact layout of alleyway, how far the path goes/went in 09 and how: jumpable fence/gate/neither? We shouldn't rule out other neighbouring houses too obvs. Was it inaccessible enough to warrant leaving a spare key to her house outside her backgarden in the pathed alleyway area rather than beneath a plantpot/similar near the backdoor? Risky. She could have left one at the Nag's even, but more likely a friend's house.
So does that suggest if he is retrieving a key and is involved in Claudia's disappearance it is more likely a spare for nearby shed/garage as ML said, which belongs to whom? Did Jen still have a copy of the house key having lived w Claudia? Did she live across the road in March 2009? Pretty sure she didn't when I worked at the Nags.
Apologies if any/all this has already been said.