I've had leaves plump back up after being dehydrated for a bit-- though they will always bear some of the "scars" of the dehydration, they did become full and turgid, mostly.
It is unlikely your plant got shriveled from lack of light, but rather, too much-- or just not enough water. Light will change the color of the leaf, most notably.
There has always been a lot of discussion about whether or not one should remove a spike from a plant. I tend to leave mine on, if in good health. I've had many phals rebloom this way along with a new spike. However, the removal of the spike can also start a natural reaction where the plant focuses attention on growing new roots and leaves. And finally there is a case to be made that cutting anything, you invite possible viral or bacterial infection. It's a judgment call in the end, really. But if the general health of the plant is not good (ailing leaves and few roots), I'd advise removing the spike. Spikes will stay in water for several weeks so it wouldn't be a total loss, either.
This is not my experience but I do know of a gardener/scientist that is working in Ecuador who has cut the end of a phal leaf, under water, and the plant's response was to have the leaf plump up a bit. He says the plant did survive and he's done this several times. Never tried it myself but you would have to be diligent in keeping the plant and water free of bacterial growth.
Regarding physan, be careful. It isn't a curative, but a preventative and I'd be willing to bet people over-use it simply because they think they're sanitizing the plant, when they could be doing more harm than good. A little goes a long way and flush flush flush!
Just my opinion on the matter... now if I could just SLEEP.