Yes, it's back. I found it while on a fed patrol and announced it on the redalert channel about 8pm CST last night.
Than how come when my fleet organized an event to engage the crystalline entity that the queue didn't show up when we spoke to it. We even had the mission up and posted and the crystalline entity queue was not in the PVE queue.
Not sure if this is the way I know how but there is a way to play the Crystalline Entity mission. Since Cryptic intends to have it 'closed' it's probably not right to share the info. I hope Cryptic will reactivate in on their own since there is nothing at all wrong with the mission.
There is something wrong with that mission: It's not suited for a public queue because some moron will always ruin it, either on purpose or by being clueless. Having it private-only was good.
It's possible it wasn't intentionally removed, but made inaccessible as a side effect of the changes to the private queue UI. Especially if it can still be played somehow.
I do hope they put it back, but IMO it should give the accolade and trophy for everyone instead of just the 1st place. It's a team effort, as much as the STF optionals if not more, so the whole team should be acknowledged, not just one with the highest DPS.