They didn't man the borders until hours later.
Are you sure about the 8am arrival of the dogs?
If I am reading the files aright, the GNR had sniffer dogs out from around 2.00am on the 4th. Throughout the night they searched ...
" the entire perimeter of the OC, in the urban area, plots of land and the nearest buildings, the officers searching all the place where there was a possibility the child might be, this area being extended later to include all of the beach zone."
Another team arrived around 8.00am.
http://www.mccannpjfiles.co.uk/PJ/GNR_SNIFFER.htmWhich illustrates the assertion that Madeleine may have been taken and hidden under a rock somewhere, perhaps the beach, and collected and moved later on ... absolutely ... and completely deluded.
The one certainty that can be taken from the GNR dog team searches is that these officers were totally professional and carried out their task with diligence.
For that reason I think had Madeleine been injured in an accident outside the apartment, or had her body been discarded in scrub-land in Luz there is a very good chance these teams would have found her.