1. The external hard drive itself has gone bad.
2. The file system on the drive is corrupted
3. The controller card (the electronics where the power and usb plug in)is stuffed.
You said that a check in disc management shows that it has no file system. Try this before you do anything else:
With the drive plugged in, open device manager.
Right click My Computer, select Properties/Hardware/Device Manager
Expand disc drives by clicking on the + sign, right click the USB drive and select properties.
Go to the Volumes tab and click Populate. Look at what appears next to Partition style: It should say Master Boot Record.
If it doesn't, then we may have found the problem. There are ways to attempt to reconstruct the MBR.
As to putting the drive in the freezer, I'd be very wary of putting a complete USB drive in it's case anywhere near a freezer simply because of the controller card inside the case. Note, I've had a couple of external hard drives go bad and I took them out of their cases, threw away the controller card and installed the drives directly into a computer case where they worked perfectly.
If we assume that the drive itself is still readable you may like to try recovering your data by using this freeware tool: Partition Find and Mount
http://www.softplatz.com/Soft/Utilities/File-Disk/Partition-Find-and-Mount.html