Stuck on a paricular bit

Hi all, i really need help from someone. Has anyone got Harry Potter and the Philosiphers stone on the gamecube? Cuz i'm really stuck on a particular bit. Its the bit where ur in hermology class and then sent to obtain the book of difindo. You go out in to the garden/forest and first have 2 take care of the troll and then get the diffindo spell book. I have done both i can't find a way out of the stupid place and back to hermology class. I think i know where i went wrong, cuz there's this bit where u find bird feed and then have the oportunity to call hedwig, but i think i called him at the wrong place, i called him at the spot where this statue of this eagle thing is where all these leaves are on it b4 hedwig removes them and the green platform things appear, i think what i should have done was to call hedwig at the point where this wooden planky bridge has sort of half appeared. And now i can't find anymore bird feed and can't go back 2 b4 i fed hedwig at the wrong juncture cuz i saved the game after i did that and now i can't get out of this forest place and back to hermology class with my newly obtained diffindo spell. I'd be very grateful if someone could help me. Thanks in advance .

Sorry m8, don't have that game.