I don’t know much about how these ads are placed...but, if you watch CBS on cable tv, isn’t it possible that the local cable company positioned the ad...making it hard for a company to know if their ad played during Letterman. This would be completely outside of a company placing an ad with CBS.
I just want to make sure the right people are getting boycotted.
You are misinformed. Local cable systems do NOT place local ad insertions on network shows like Letterman. The ads come from the network or their local affiliate.