The Lemon Fool

Makes you realise just how many wide open spaces there still are, that we are only finding out about this 3 months later from recorded data.

Slarti

There was a (probable) full-on nuclear explosion in the South Atlantic in the late 1970s detected by US satellite(s) - don't think they ever worked out 'whodunnit'
I would guess modern monitoring satellites would have picked up this event, although it wouldn't have the typical double flash of a nuke