A mention isn't even necessary. Imagine being Light getting his source of information from the internet, his ISP has a small incident with a lightning storm and they lose connectivity completely for a few days while things get sorted out. Involuntarily information has just been leaked irregardless of all other protections, the deaths of criminals would have been disrupted. In this situation you would ideally be working to some great latency of days or weak to give a buffer of information. It's talked about in the first few episodes that he works ahead in case of sickness, but it's not mentioned after that, possibly because it means he can't use those events as cover for on the spot murders (which would stand out from week old information based murders).