Agree with D_Know_WD as it might just be you damaged the external enclosure. Buy a cheap USB enclosure for $10 and take the hard drive out of your current enclosure and try it in the new one. Happened to me recently and the drive was fine but the internal board of the enclosure was damaged in the fall.
If you still cannot get it to read then try a data recovery program, something like Stellar Phoenix has worked for me in the past. I am assuming this is a Mac formatted drive, if it is NTFS then you can use something like GetDataBack.