Matt and I have been trying to figure out what happened. He does have a tendency to poke his nose places it doesn't belong, but we don't think any of those places have edges sharp enough to cut his whiskers, nor do they appear to have been singed, which is something that Taylor has done before, sticking her eyebrows into lit candles.
All in all, a mystery. I hope they grow back soon. Until they do, however, I will refer to Chuck as "Half-Face."