Ok so I've just been grinding the latest lost sector on the EDZ (Excavation Site XII) on Legend for a pair of Phoenix Cradle as it is the only pair I don't have in my collections. However, after 150+ runs I received the sum total of ZERO! I got all other exotic boots for my titan - and plenty of them - but to get absolutely NONE of the cradles makes me question the lost sectors (not to mention my sanity). My game history from the last 20 ish hours is just lost sector runs (excluding the transition to patrol). I probably know the answer already; my RNG luck is the worst, but I figured I'd ask on the off-chance there is a bug. I'm hoping for the former so I know I haven't just wasted my time, either way I am done with lost sectors for a while!
Pretty sure the lost sectors prioritise exotics that you don’t have. After that, just pure RNG, and some bad RNG in your case. RIP