We were married 3 months ago. We were given a small gift and an IOU for a gift certificate from one guest. The gift certificate has not arrived so I don't want to send a thank you for a gift we don't have, but I feel bad that it's been 3 months and I've not sent a thank you note for the small gift we did get. What's the proper thank you note etiquette in this situation - should I write a thank you for the gift we received and just not mention the gift certificate that never arrived?? Thanks!