No, but you don't get your move action back if it negates your entire movement. Ask fighters about that one. Negating an action doesn't mean you haven't spent that action, or that you haven't used that action. And no one is claiming that, either.
The reason should be clear, a power is used as soon as you use it regardless of how it ends up being resolved.
The Reliable keyword says this is also incorrect. The keyword shows that a power's 'used' trait can be dependant on the resolution of the action itself. If, through some means, Crescendo Blade got the Reliable keyword then it doesn't become used, then unused if you fail to hit.
Reliable said:
If you miss every target when using a reliable power, you don’t expend the use of that power.
If the power were already used, then Reliable couldn't work. Reliable does work, which means that the power is not already used. Used, in the case of Crescendo Sword, obviously means 'expended'. And if it didn't, then recovering the use of Crescendo would be meaningless, as you'd expend it after resolving -anyways-.
To support your argument this quote would have to say "while using", it, if anything, supports mine.
Your premise was that 'using a power' does not exist. That was directly disproven by counterexample. The word 'while' is a strawman you're inserting in to make it seem as tho your premise is untouched, as is the idea that there is no 'using a power' state by claiming it is inexact.
However, the english language has a clear definition for it. It is called 'Present Tense'.