You can't recover the data if the system is not detecting the drive, that's why wise people keep backups of everything on a second or even a third drive.
For a non-detected drive, the only way to get any data off it is to take it or send it to a data recovery specialist service, which is very expensive (another reason why keeping backups is so important).
The "freezer trick" is a myth, but you've nothing to lose by trying it