Let me see if i can take a crack at this and not mess it up.

The tissues of the corals are clear and are colorless while the zooanthelle of a specific coral produces the color variations that we see. The white that you see in after a coral RTN is the calcerous core of the coral through the translucent tissues of the coral. When a coral is bleached its zooanthelle has evacuated the coral and died( Due to whatever circumstances) however the coral can remain allive as it not only lived off of zooanthelle but also with filter feeding.

The reason zooanthelle share a symbiotic relationship with a coral is that it provides it with a protected shelter and also provides it carbon dioxide through photosynthesis.

So.... I would say the answer to your question is yes they could still be holding on however it is inevetible since the zooanthelle is gone that they will die.

This is what I think happens and is by no way for sure, sorry to be the one that says it......