future252

Guys
Another wee problem and hope someone has a solution for me. Have recently finished en-suite in my own house (thankfully this hasn't happened with a customers tiles!) and had used the washboy to go over the grout - so far so good! Unfortunately before I got finally finished I had friends appear unexpectedly, so the washboy was cast aside while I was entertaining. Anyway, by the time I got back to finish off (a couple of days later) the grout that was left on tiles on one part of a wall won't come off.
Any suggestions????????