Drive not in device tree

I have an external HD hooked into my Macbook. Shows on my desktop and works fine. But for some reason it no longer shows in my device tree. Also had up until about 3 days ago when I accidently unplugged without ejecting. I tried to shut down and all other basic type things but cant seem to figure it out. Again, the drive works fine and shows on desktop just not in device tree. Also added other devices just to see if tree was working properly and it is. Any one have any ideas? Maybe I messed with associations.

Thanks

Mike W