Getting back to the original question I have found an easy way to find the buoy....
When you get to the nav point with all the unknowns destroy all but one of the nephilim ships, whilst Stilleto is busy attacking the remianing ship turn off your smart-targetting, and reverse target the unknowns (shift-R I think). Stop at the first pointy unknown that you target, go and fly close to scan it and it should be the buoy. I've tried this loads of times and it hasn't failed me yet
Shift-T is right. Although I just go around shooting the pointy buoys, the one which doesn't blow up is your target. Wish all Confed equipment could be built with that stuff.