Hi, sorry for the trouble. Berryboot (WD version) will install to an unformatted drive or a drive with data on it. It sounds like Berryboot is partially installed and is looking for the specific disk. You should re-image the SDcard (you can download the zip file at this page: http://wdlabs.wd.com/downloads/). Use SDFormatter tool to reformat the SDcard (with options “Full overwrite” and Foarmat Size Adjustment" enabled): https://www.sdcard.org/downloads/formatter_4/ . Then unzip the zip file directly to the root directory of the freshly formatted SDcard, using 7-zip (http://7-zip.org). You can leave the PiDrive as-is, the fresh copy of Berryboot will enable you to select the installation target (“sda…” is the PiDrive) and warn you that it will overwrite existing data.
I’ve occasionally had trouble trying to install an OS where it takes a long time, or there’s internet connectivity problems with the software repository. Usually it’ll eventually give an error message. In those instances I would just wait awhile and try again. Not sure if this could be what you experienced, however.