I vaguely recall at the time, reports of paedophile rings operating throught Portugal and beyond. Perhaps, to the local Police, it was an all to common occurrence, and they treated it like they would any other missing child case

Lets say you're a local Police Chief, and every Friday a local person is murdered with no motive and no evidence. Then one Friday, a tourist rather than a local is shot, no obvious motive, or evidence.
Because it's a Friday, you treat it as a normal routine Friday murder, no leads, no suspicion, but suddenly the relatives of the tourist insist that not enough is being done to catch the murderer, politics get involved, and of course the media...
You have to do something, so you wind up going through the motions for a quiet life, and a year later, you're no nearer a result so you close the case, and deep down you suspect that it was simply another regular Friday murder.

I suspect that is where the Portuguese Police got to...