My brother is a UNC Fan and stole my hat.?

Ok, in 6th grade my brother stole my duke hat that i got from confirmation. So 5 days ago(im in 8th grade now) my grandfather gave me a duke hat, My brother said he would steal it just like he stole my other hat. Hes 16 but when i say he stole my hat he says he didnt. How do i get it back