How to find recently connected external disks? Bit of an emergency so any help really appreciated.

I am trying to work out whether or not the there is a way for me to see the details (specifically names) of external drives that have been connected to my machine in the last 6 weeks. Basically a hard drive with confidential information has gone missing and I would like to see if it was ever connected to my machine, does anyone know how or where I can find this information?
The following commands will show you all the external disks which were mounted upon your Mac during the last 7 days (unless you modified the conservation limit of system logs):

grep mounted /var/log/system.log
zgrep mounted /var/log/system.log.*



If you would like to increase your auditing possibility on this sort of event, here is the way (for the ones at ease with the Unix talk):


open the newsyslog configuration file:

/usr/bin/sudo vi /etc/newsyslog.conf

change the following line:

/var/log/system.log                     640  7     *    @T00  J


with:

/var/log/system.log                     640  30    *    @T00  J


(which means keep 30 versions of my old /var/log/syslog files)
save this modified /etc/newsyslog.conf.