What are you going on about? Kate left alone. Gerry was at the table. No sighting happened until they were out searching after the alarm was raised.
(By Amaral's theory)
Kate finds
the body (of her loved and cherished daughter).
Gerry is oblivious and unaware in the restaurant.
Kate pulls it together, waltzes back to the restaurant, communicates devastating news to Gerry.
No one (else!) notices.
They (Kate and Gerry) hatch a plan.
Gerry leaves the restaurant.
He scoops up the body (of his loved and cherished daughter), waltzes it past the noses of the Smiths, and conceals it somewhere on the beach.
Meanwhile, Kate returns to the restaurant, simulates an alert (and no one notices Gerry's absence).
We haven't even got the bit of what the McCanns are supposed to have done with 'the body' in the 3 weeks after those events before hiring a car to drive 'the body' to Huelva, Spain.
Far the most plausible explanation is PJ Inspector Carlos'.
At the time of the Smith sighting (and Kate's alert) Gerry was in the Tapas Restaurant.
That's what Inspector Carlos wrote.
Every reason to suppose he knew what he was talking about (Inspector Carlos) .....