Sounds like it has gone past the point of no return. Ericaceous plants are THE most unforgiving if they don't retain a moist rootball.

If you let the compost dry out to the point where it shrinks, it's necessary to put the pot in a bucket of water, so the soil is completely submerged. After a half hour or so has passed, and there are no bubbles coming up, the soil should have swelled enough and it can be taken out and allowed to drain. That will give it its best chance of survival, but as Fractal says, Gautheria, like most members of the heath family, isn't very forgiving.

It is obviously growing in a peat based compost. When peat dries out it shrinks and it is difficult to get it wetted again. This is another good reason for not using peat! It looks as if the Gautheria id dead.