How did you know whether your character was sneaking or not? If you assumed your sneak roll failed because you saw this message:
Code:
> sneak
You attempt to move silently.
You no longer feel stealthy.
You should know that all this means is that you made a skill check while your character was already stealthy.
The second line has no bearing on whether or not your character is still sneaking. It's just the message that your old sneak affect was canceled by the new skill check you just did.
On the other hand, if you saw:
Code:
> sneak
You attempt to move silently.
Then you made a skill check while your character
wasn't already stealthy.
Either way, you'll never know whether you're actually sneaking or not unless you ask someone else to confirm it. (Although with innate skill it's generally safe to assume that you succeeded.)