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Providing your Analytics script or TAG manager is still using the same code then the tracking should remain in place and always be available. A drop would indicate as per Gaston's response that the code was inaccurately implemented or missing. Did they change the analytics whilst in development, was it missing when going live? A good way to check your analytics tag is implemented correctly would be to run the following plugin for chrome https://chrome.google.com/webstore/detail/tag-assistant-by-google/kejbdjndbnbjgmefkgdddjlbokphdefk