Normally, these problems came from factory and you should be detected the first time you start up your computer. If you haven't noticed anything strange in the display, don't worry and keep using the Mac because it's working correctly. Refurbished computers have been repaired by Apple and have got the same warranty as a new computer, so there's nothing to worry.
If you want, you can get AppleCare to extend your warranty, recommended in the case of your MacBook Pro with Retina display because a lot of hardware is soldered and repairs might be expensive
You have a one year hardware warranty; if you buy Applecare, that is extended to three years. Either way, it should be plenty of time to see if there are any hardware issues. In addition, most users with the display issue see it sooner rather than later, so if it pops up inside 14 days, you can either return it or exchange it.