Item Bug (item is randomly selling)

Alright. So I was playing a ranked game. I built a PD, and an IE. I was pretty fed, so I went to buy a Mercurial Scimitar. I got it, and then when I went to fight, I didnt put out any damage, and then I died. When i looked at my items I noticed my IE was gone. Wtf? I didn't remember selling it, bc why would I sell my IE? This has happened a few times :(((