How long have you had it?
Is it from this past Christmas??
If yes, then it will most likely grow more leaves in the next few months. 12 leaves do not appear all at once.
For example, mine usually send up 3 or 4 at the same time right after blooming (or some at the same time as flowers). Then more leaves follow one at a time.
If you have had it over two years and it is still growing that way, I would toss it.
Amaryllis being so common and there are so many exciting varieties to try.
I recommend buying the largest possible bulb from a good online vendor. That way, you get a good bulb and the good bulb will stay that way for years.
If you are buying from big box store, try not to get the last leftovers. It is just not worth it.
If you choose to buy them from big box stores, try to get them as early as they are available and plant them right away.
Often you will see the qualities are not that great.
Red blotch diseases are all too common, and the bulbs are already sprouted in that paper box all distorted.
If you can open the box and check the condition of the bulb, then try to get a healthiest possible one with no red or brown marks. Avoid soft one and only pick firm one. you don't have to squeeze too hard. lol
Anyways, when you get it from a good source, you don't have to worry about all this.