It must be on because after pressing the shutter a second time it did take the picture and I can see it on the display. The problem is that when I look at my menu under "mirror lockup" and click it a message comes on "cannot register more items, delete an item and then register" so I can't see if it's on or not and if it is on I can't change it to off. If I delete an item can I get it back or is it then gone from the camera?
You may have to do a full reset to the factory configuration. This is done by removing both the main battery (or removing the "grip" if you are using one) and then also removing the disc-shaped memory retention battery. After waiting a few minutes, reinstall them and the camera should be returned to the factory-new configuration.

