License keys and software installations don't have any technical relation, they are being scanned independently from each other. Please find an article
here which describes this difference.
In many cases the installers of software don't remove old license keys from the registry of your client computers. Therefore Lansweeper still will scan it. The only way to resolve this would be to manually remove old license keys from the registry of the client computer.
Office 2013 keys are not always stored in the registry. In this case there is no way that Lansweeper can scan it.
This article describes it in more details.
