The theory is that the drive platters and arms will contract slightly in the cold, overcoming any physical issues such as chips, debris, and troughs in platters caused by head slaps or malfunctioning actuators. Of course this is only good for as long as the components remain cold enough, so the time window is very much limited. I suppose if you have an overheating drive it might also give you an extra few minutes before the critical temperature is reached. Either way I've not seen it work personally, and only heard of it working a handful of times out of the couple hundred failed drives I've helped people through over the years.
If you've got a toasted circuit board, thrown bearings, or severe platter/head damage, it's not going to save you. Also, some drives that fail to initialize or perform properly due to physical issues (e.g. chittering drives) generally respond better to being mounted upside down or sideways. I've had a number of these over the years as the units reach EOL and the remounts buy a few extra weeks of operation. Stuck heads may be freed by hitting the side of the drive firmly with something hard but not overly massed, like a screwdriver. That I've only done once, to no good effect; the drive spun up after that, but was still beyond saving.
For those in high-humidity areas, be fast about it.
. In any case good luck with the data retrieval.
