I code in a variety of languages and every time I use .indexOf(), I can't remember if it's (needle, haystack) or (haystack, needle). Of course, my IDE shows me the correct way and I go with it in 0.3 seconds.
On a whiteboard, if I were marked down for getting that the "wrong", I don't think I'd like to work for those kind of people anyway. I have no interest in memorizing the exact syntax of every standard library call in every language. When I can look it up almost instantaneously, my mental efforts are best spent elsewhere.
I don't care if they can't remember order of parameters, or really even the name of the methods. But if you can't write syntactically correct code without an IDE, it seems like a problem.