coloring outside the lines

prison guards recently discovered an inmate with these pages from a coloring booking coated in a drug called suboxone. what makes me wonder is how they figured out it was coated with drugs, did they catch him with it in his mouth giggling? it really makes me wonder.
here's the pic:

http://www.msnbc.msn.com/id/42321254/ns/local_news-philadelphia_pa/