Yet another layman's view.
LOL, Slarti. Even a layman has ...
(a) common sense
(b) the ability to read and assimilate information
One source of the information (b) at which you scoff can be read here ...
5.9.
Method of IndicationIt is recognised that in the operational environment dogs should not be encouraged to
retrieve, mouth or interfere with any item of property. This ensures that evidence can
remain in situ prior to any forensic analysis, photographs etc. It also avoids concerns
regarding cross contamination. It is therefore recommended that all police dogs have a
no contact, passive indication upon locating property. The dog should quickly learn to
understand “I search, I find” and then receive a reward. This reward is normally a toy
delivered once the correct behaviour has been established.
https://cinotecniamilitar.files.wordpress.com/2015/02/201103uopdogsmog1-1.pdfAs far as (a) is concerned ... logic dictates that it is not a good idea to risk contaminating evidence (or being contaminated) ~ hence protective clothing, gloves, masks, evidence bags etc ... and I would imagine that were one a handler with a trained explosives finding dog one would be particularly diligent in ensuring that the dog was trained to the nth degree in not picking up what it was trained to find and throwing it around the place.
Anyway, following the link I have provided will enable even a layman to have a greater understanding of precisely why the dogs visit to Praia da Luz was of no significance either to finding what had happened to Madeleine or to solving the case.
Worth reading just for the explanation of the value of two
handlers working a scene.