I think people still underestimate the elements, particularly if coming from a temperate climate country with little experience of hiking in adverse conditions.
He would have been dehydrated from alcohol and even 2% dehydration starts to impair cognitive tasks - we heard via Lucy’s account of the phone call that he needed a drink AND also that he was lost and didn’t know which way WAS back on himself. Link to resource
Cognitive performance and dehydration - PubMed
The tourist page says the Teno national park is full of ravines, gullies and is over 8000 hectares - the same size as the Forest of Dean. The tourist website also shows the photos of why this area including masca gorge is so deadly
Masca Gorge | Camino del barranco de Masca
Being searched by what, 50 people? And you’d have to be within a bush or two of the body to see it. Jay was wearing muted colours, and unfortunately skin becomes black by about day 3 of death in arid exposed conditions (I don’t want to link to this resource out of respect to friends and family but it is easy to search on Wikipedia if you are interested to learn further). He will not be especially visible, and is likely to have crawled beneath vegetation for shade or if he fell and hit his head, he may be down a crack, outcrop or gully.
I don’t know how far he may have walked but there is mention of volcanic rock outcrops jutting out into the sea on descriptions of Teno rural park.
As many searchers are volunteers and not professional search and rescue themselves, they will be limited by the terrain they cover and the distance also - furthermore they will not be thinking like an anxious, dehydrated, disorientated teenager after a night of drink, lack of sleep and the start of sun stroke etc