what does "tested 0 (zero)" mean?

As said, it likely means no evidence of disease. Not cured, just no evidence at that time.

The standard of care is not to do scans or tests to monitor for distant recurrence (aside from what you may have had as part of your original diagnosis work up) unless you are symptomatic. Some oncologists may differ...but they seem to be exception, not the rule. There are a few reasons for this. One being risks of radiation from regular scans, as well as anxiety of testing, and possibility of false positives, etc. Mets can show up in bones, lungs, brain, etc....they cannot predict where so that would mean a lot of testing and exposure. Blood markers are known to be a bit unreliable. More importantly.....there is no added benefit in screening before one is symptomatic. It does not add to the length of survival or improve quality of life. 

It is best to be aware of symptoms and see your oncologist if they persist, for more tests. Here is a link to symptoms and possible follow up tests:

http://www.breastcancer.org/symptoms/types/recur_metast/where_recur/metastic

The woman on Little Couple had a different kind if cancer, so it is important to realize that follow up is not the same for all kinds of cancer, survival rates different, recurrence risks different, and follow up tests may also be different.