It could be flour that has had extra gluten to the flour added .It makes the flour stretch , used a lot in pizzas the fact the you found it in the freezer would be right as with gluten flour you can refrigerate for around 24 hours
The dozen or so references on the web I looked at confirmed this. It is likely vital wheat gluten mixed with water to form a dough, ready to be cooked into Seitan by boiling or baking.