Intel Mac :: Storage For Time Machine Backup Cannot Be Found

Late last night I accidentally ejected Time Machine from the Devices section of the Finder window. I've now spent half a day trying to get the computer to recognise my external hard drive again as attempting to use Time Machine results in the message "Storage Machine for Time Machine backup can't be found." I can find my WD desktop 1TB drive with Disk Utility but not in Finder. If I click on the WD Ext HDD 1021 Media in Disk Utility there is the option to Verify in the top menu, but nothing happens when I click on it. All the options verify, and repair are greyed out. I've checked the computer hard drive and done the verify and repair disk and permissions process.

I've turned off the computer, disconnected the external hard drive, turned off time machine, then turned everything back on but still can't get the external hard drive to be recognized. This is extremely frustrating and I have run out of ideas. I know it all started when I clicked on the eject button for the external hard drive in the devices section of the finder. Such a simple mistake, but I have searched everywhere online and can't find a resolution that I can actually try. I can't verify and repair the WD hard drive if these options aren't available in Disk Utility.

Info:
iMac, Mac OS X (10.5.8)