There isn't the money available to search every 'possible' crash site. We could search this 'new' 25,000 km3 area and still come up with nothing. Then the boffins would come up with another new area,and so on. The cost/benefit equation is not very promising.
If a wealthy person wanted to donate money to fund more searches,that would be good but I think it's time to let it go,accept that we'll never know what happened and move on.