I have an external that showed up the first time on the left side bar but now cannot find it and does not show up anymore. It is an newer hard drive from a now broken computer. I have tried to do as much research as I can but obviously am not good with computer stuff. How do I search to find this file? I have looked at everything in file systems. This is ubuntu 12.04lts.

Try going opening "Computer" or go to "Media"
another thing you can do is go to Disk-Uility
You can try fdisk -l.
Are you trying to format this drive?

I looked in computer and have no media to select. This hard drive was used with ubuntu previously and I pulled up all the pictures once before. I read something about once unmounting the external you have to know where to go to pull it back up as it does not do it automatically again. Any other suggestions? Why does it not just show up like any other USB chip? I know it is somewhere and this seems like an easy fix I just cannot figure it out. Other searches show people with this problem as well, I just cant understand it. THanks

media is under / or filesystem
If I have a hdd that doesn't show up after boot I mount it thru disk utility.

As stated Ubuntu will automatically mount an external drive under /media directory. The quickest test would be to unplug and reinsert the USB drive connector. If it still isn't automatically mounting then take a look at the output of the dmesg command via a terminal window. There could be some error messages related to the drive.