What does a Master skill's (1 use) reward mean: does it revert or disappear?

Question

Accepted Answer

It is a one-time use of the Master level. Afterwards the skill goes back to the level it had before, and if you did not have the skill it is removed. You choose when to use it.

Tales of the Arabian Nights (2009 Edition)

What does a Master skill's (1 use) reward mean: does it revert or disappear?