Peter does not appear in this episode, and Prof. Maxwell is banned from the Magical Library. To research the keys to the lost Hidden Temple of the Purple Lotus, he needs to search through the very sizable aisle pertinent to keys. He figures it'll take him a month of reading to get through it. Peter once digitized the library and is not present at the magical games (thereby presumably available). Maxwell should have obviously contacted Peter, but the idea never arises.