Have any of you had this happen before? What's the best way to proceed?

I ordered two sizes of a dress (L and PL) from the Anniversary sale, and only one size is in my box although both sizes are show up with the same tracking number and both sizes are on my return label.

Is there a way to handle this without a phone call? I'm super busy this week and don't have time for a call, but I don't want to let time elapse because I'm nervous I won't be believed that I didn't get the item so I think it is important to notify straight away.

thanks for your insight!
Traci