They know where it is. The problem is the radioactive part is surrounded with lots of high explosives. They could recover the radioactive part but if they trigger the explosives they kill people and spread the radioactive parts over a fairly big area. No danger from it actually triggering a nuclear explosion though.
Devices of this era didn’t have insensitive HE, and a number of incidents occured where in crashes the explosives cooked off killing fire crews.
Just leave the thing where it is.