Quest Help please!!! :(

Well i am at the end of gloruis memories and i did the potion but i forgot the yeti hair somehow i lost it. and i went back to see if i can fight the yeti agian but hes not their! what do i do? is it possible to get the yeti hair or am i ever going to be able to finish the quest?

 

Yeti hair may be obtained by killing either Nial Swiftfling or the smaller, level 90 Yetis encountered in the Trollweiss Dungeon.