A someone else has said, floppy disks are not very reliable.
Also, a diskette created on one computer may not be able to be read on another computer.
Firstly DONT PANIC, and DONT FORMAT the diskkete.
My guess is the data IS still on the diskette, so what you need to do is try it on a few different computers.
If you can take it back to the one you did it on originally that would be best. If not try friends and neighbours PCs till you find one that can read it, or maybe your friendly PC shop may help.
In future store data on a USB key, picture here
http://opensource.bureau-cornavin.com/belkin/u sb-key.jpg
You can buy these in any computer shop and they are very cheap (�10 or so).
You plug them in a USB slot in your computer (most computers now have a USB slot).
It is then very easy to move files from a hard disk to a USB key, or from a USB key to a hard disk.