@ Dai Farr 'I flew SAR on Air India 182 back in 1985'
The return on that aircraft vanished at 07.13GMT. An emergency was declared at 07.30GMT and SAR found floating debris at 09.13 GMT just over 120 miles off shore. The technology they had back then was primitive compared to today, yet wreckage location only took a matter of hours.
A mid air disintegration leaves sizable floating wreckage and later washed-up debris. From my involvement the problem with the smaller washed-up debris was the general public didn't recognise them as belonging to an aircraft.