vincevincevince - 2:32 am on Nov 1, 2012 (gmt 0)
I strongly suspect your webhost did it. Log files, especially those which are growing fast, are often problematic for hosts without adequate storage and log rotation systems. Quietly redirecting them to /dev/null does away with the need for rotating or storing them.
You should be able to check the last modified date on the file and confirm if it is the same date that you installed osCommerce.