It could be the read/write head had been damaged so that it might not be contacting the platter correctly. Also it could be the drive magnetics were wrecked, but physical damage from being thrown around would be attributed the read/write head being damaged, and that would normally be associated with a hard clicking noise while the drive is in use. I would take it to a Best Buy or any local computer repair and see if they can retrieve the data, and place it on a new drive.
If you are traveling often it is best to get a slim external hard drive like a Western Digital Passport Elite or a Seagate FreeAgent Go series drive. They are slim and usually USB powered.
If you have anymore questions or comments about my answer, please feel free to contact me and I will gladly reply.
Have a nice day
How did you fix it?
If you were thrown around a lot, how would your memory be.
The HDD may have some damaged sectors, so if you 'fixed' it with CHKDSK /F, the damaged sectors are marked as unusable by the OS (Operating System) but leaves the others as usable. There is no way to restore bad sectors.
maybe exposed to high magnetic field.