A company is fully entitled to make people redundant if the job no longer exists, even if they are profitable.
If your job no longer existed because they had lost business, they were entitled to make you redundant. I don't think that getting a new client afterwards, changes the fairness or otherwise of your redundancy.
Have you spoken to them, either formally or informally? Could you apply to get your job back? If I was in their shoes, I would probably offer you your old job back. If you decline it, it would weaken your case.
Brendan