I was doing the scavenger's den lost sector. After getting the new warlock boots I switched to titan. Whom had all exotic armor except for the new boots. After 15 completions an exotic finally dropped except it was the Phoenix cradle an exotic I already had. Just to be sure I checked collections and it was not in new.
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Hey there. Unfortunately the lost sectors are not guaranteed to drop the new exotic before other exotics you already have—it just has a higher chance to drop the new one. Keep at it and it will drop eventually!