I read your post carefully twice...I was especially interested that you wrote, "I understand that this was an honest mistake and one that I should have caught when reviewing the documents. We typically take two to three cruises a year."
So...you're NOT new to cruising, typically taking two to three cruises a year...
and you admit that YOU should have caught the mistake when reviewing your documents.
And it's RCCL's fault that you missed your cruise because......?