The ingredients I am referring to are lacewing flies and boomslang skin. The two ingredients that are usually mentioned in the brewing of the Polyjuice Potion.
However, in the Cursed Child, Professor McGonagall mentions that these two ingredients were stolen from the school's stores, but since they are not on the "restricted list" it wasn't a big deal.
Harry and Hermione do not make any connection even though they have brewed the potion before (Chamber of Secrets), been fooled by it (Goblet of Fire), and used it as a battle tatic (Deathly Hallows). Snape even accused Harry of stealing the same ingredients and saying he was going to figure out why Harry was brewing a Polyjuice Potion.
I think there are two options here...
- The "name drop" was a clue to the reader that Polyjuice was afoot and not all was as it seemed.
- lacewing flies and boomslang skin are common ingredients.
I am looking for proof of the second option. Are there any other potions known to contain these ingredients? If not, why did none of our heroes (who again are very familiar with the potion) not make the connection?