The guesses on the forum were possibly Sumerian or Celtic, but I don't recall the scoobies coming to that conclusion. I know they talked about star charts and the date, but that even came down to guessing. In the realm of the series, it was probably better that they didn't decipher it. To do so and for Nick to continue using the stick despite their warnings would have portrayed him as arrogant and ridiculous.
The best way to frustrate a cyberbully is to ignore him.