I would email them about that or look at their FAQ section.
That's happened to me before, but since most of the titles I have in my queue generally arrive within 1-2 days (both to and from), I haven't ever found myself jumping at the bit waiting for a title to arrive.
I joined Netflix because I consistently had late fees at local video stores and at the time I joined, most video store chains didn't have a wide enough selection of DVD titles. Because Netflix has been able to "kill two birds with one stone", I cannot remember the last time I rented from a store.