1) The pinger/wreck is a bit deeper than 3000 feet.
2) In the time it takes to get to the oil slick, it will have drifted and over time spread and dispersed. As I understand the history, there were in fact patrol planes and aircraft that did take a look at the oil slick, but the Tech Log thread has waaaaaaay more info on that.
3) P-3 dropping some LOFAR or VLAD passive buoys ... might that have detected a ping? Not sure. Maybe, maybe not. Not sure if it was requested, or such missions flown. I assumed that Brazil has maritime patrol aircraft like the P-3. If they wanted US help, they'd have asked for it. I'll try and find out from a few old Navy friends if any US P-3's did acoustic search ... may not be able to come up with anything.
4) Time to datum. In any search mission, you first have to get to datum (or last known position) and then come up with a scheme.
More later.