I am not sure how ebay are going to know where your parcel is

Have you looked at the tracking number on the Aus Post site to see what it says?

Did you message the buyer and asked if it arrived ok?  (many many buyers do not bother leaving feedback to let sellers know things have arrived and they're happy)

Ebay staff do not read here, so they are not going to see your post or your concerns 

What happens when you try using the help and contact button?