Mail in coupon question

[dohc76]

I just bought a set of Zildjian cymbals for my son. On the box it says there is a mail in coupon for a free 18 inch crash cymbal. I ask the sales person if the coupon is still active and he say yes. There is no date on the box to indicate an expiration date of the offer. Get the box home and open it up to find that the coupon expired yesterday. I plan on calling Zildjian tomorrow to find out what I should do. The cymbals are still in the box. In my opinion I should still be able to collect the free cymbal based on the fact that the packaging did not indicate an expiration date.

Do you think I am correct?