I think when a child is missing with no apparent evidence of an abduction the alerts, when put in context, carry slightly more weight than the evidence of life on any other planet.
In context, I don't see how the alerts mean anything significant.
Eddie could have been alerting to:
- the scent of something that had been in contact with someone who had died;
- the scent of anything other than the physical presence of blood (if one is to believe that Keela is always accurate);
- the dog's perception of what the handler was tasking him to do.
Even if Eddie had reacted to the lingering scent of some decomposing substance, without corroboration, it could have been anything that had been removed even the week prior to the search. And the apartment had been let out just prior to the search and the statements of any post-disappearance occupants aren't in the files, as far as I'm aware.
He could have been reacting to anything.... even a dropped bandaid that had been removed after the previous occupants had moved out.