[Guille]

I can't assure that we are missing any senses, but I am 99.9% sure (with an error margin of + or - 00.1%).
In the tsunami, the animals started to run away from the villages near the coasts in Thailand, etc. They felt it, and we couldn't.
The proposition of the blind is good. Also, I always refer to humans as having 6 senses. The sixth sense is our mind. My definition of sense is:

"A sense is ability to feel or perceive the world"

And, let me give you a proof of the mind entering this definition: I can see a book in front of me; it is on top of the table. I can only (and only!) see three of its faces. I can't hear or smell the book. I can't touch it because it's too far. I can't taste it because it's too far. So, what I perceive of the book is the three sides I can see. But, as all of us know, a book (normally) has six sides (top, bottom, front, back, left, right). And, still I can't perceive three of these six faces; I know there are these three faces. I know it! How? It’s because I have another sense - my mind, which is thinking. My mind did its work: got to the "google" of my memory, wrote "book", and searched. The memory started to put the matches with the entered word in front of my consciousness. And my sub-consciousness was there to go covering the book matches: if 10 books passed, and they all had a front (let's say I can't see the front of the book in the table), then, the sub-consciousness matches it completely. And so and so, until all the general properties of books are matched by the sub-consciousness, then the consciousness is given the info by the sub-consciousness, and now I realize that it is a book-like object that is on the table-like object in the room-like place.

I know it's long, but it is worth it to read this.

So, I believe that if there is a sense that we still haven't realized that we have, then the probability that there is a sense that we don't have is much higher, and thus, there must be various senses that we don't have.