After 6 busy months I finally got all of our thank you notes sent out... or so I thought. I wrote a few here and a few there over the 6 months since our wedding. I had a checklist on my computer and deleted the gift giver after a note was sent. I recently found, amongst paperwork, an invoice from a gift sent in the mail from a friend. I can't remember if I sent her a thank you and I can't check to see if she was on my list because I deleted it! There is a chance I received the gift with the invoice, put it aside intending to put her on my list and never did. Is there a polite way to ask if she received a thank you form me without sounding ungrateful? Please help!