Deleting

The easiest way to just to select the chart object and press the Delete key.
If you ever have charts (or objects) on a worksheet that you can't actually see the easiest way to find them is to select an object (by holding down Ctrl and selecting) and tab through all the different objects on the worksheet.
If the chart is on a separate chart sheet you can delete the sheet as you would delete a normal worksheet.
Just select the chart sheet tab , press the right mouse button and select Delete.