Sorry, but yes, it is fair. It is the work that is graded, not the person. The comments are devastating, actually. I doubt that there is much you can do now, other than assure you don't get into the same situation in the future.
You can, of course, ask the professor for a second chance. I can't guess what the response will be, but I think you have the right to ask. Under the circumstances, it might be granted. It would mean more work for you, of course, but that might also aid in your overall learning.
If you didn't understand the assignment and needed help then you should have been seeking it along the way. Prior to turning it in, you had some leverage in getting help from the prof since you were working alone.
I don't know why the prof set it up this way. A single group of three might have been a better solution. Asking for a volunteer to work alone might have been a better solution.
But, for your own educational purposes, try to understand where and why you didn't meet the standard.