Stalled Fermentation

Hi Everyone - I tried a recipe on MoreBeer! "How to Make Alcoholic Ginger Beer.” I’ve never had a stalked fermentation but I sure do now.

I brewed a five gallon batch a bit in the blind as my hydrometer broke on brew day.  I followed the recipe, used yeast nutrient, and used two packets of S05 dry pitched into the “wort.”  I was unable to read my SG.

Two weeks later, I took my first reading (new hydrometer) and was suprised to find FG = 1.020.  The recipe says were targeting "a FG around 0.996.”

The recipe calls for plenty of organic cane sugar (no DME), lots of peeled/diced ginger, and zest/juice from 5 pounds of limes.

Thoughts?  What would you do?

Here is the recipe: How to Make Alcoholic Ginger Ale | MoreBeer

No idea, wild guess something to do with the yeast, following.