This bug occured in singleplayer mode when playing the .63 stress test version.

I went to a military complex and found USMC pants. I dragged and dropped all my inventory items that were in my cargo pants in the USMC pants, and I went to put on the item (I am not completely sure if I accidently put the item in my hands). From that moment on the military pants were stuck in my hands, with no option or method to remove them out of my hands.