Charles Widmore was an Other, so he likely knew about the Black Rock being on the Island. Since it's also likely he could've known the Island had moved or was moving, he could safely give the coordinates he acquired from the first mate's ledger to the salvage crew, knowing they wouldn't actually find the Island. Instead, it would act as an authentic salvage mission leading to the site of the staged Oceanic 815, thereby looking like a convincing discovery.
In Chapter 3, we saw the ship having major electrical problems. This could be the day that the hatch imploded (67 days after the crash).
Even though the hatch imploded in the middle of the day, it can still be consistent with the electrical problems occurring during the night because of time dilation on the Island.
These electrical disturbances could have also occured on Day 58 when Locke first saw the timer reach zero in "One of Them".
The media seems to frenzy over the coincidence that Sam Thomas was on board the ship that found 815. This way more people believe that it was real and not a set-up. At the very end, it seems that Sam may have come to this realization, that he was led there to make the finding of the 815 wreckage believable, based on his reactions to Talbot's interview.
Sam Thomas' contact was part of the set up, following the orders of Charles Widmore in having the fake wreckage discovered. The fake contact was needed to make it believable to Sam.