Direct Mail Company Question...?

I hired a company to print and mail out postcards for an event my company was putting on. The company told me that the postcards were mailed out on the 28th of August and we were using USPS bulk mail which is 6 - 12 days for delivery. Well I have my address on the mailing list along with 3 other friends so we know when the postcards are being delivered. We have never received the postcards, nor did anyone at the event turn a postcard in for free admission. We sent out 5,000 to a very targeted group of people. Not one was turned in. How can the company prove to me that the postcards were sent and were sent on the day they said they were sent? What kind of document do I need to get them to provide that the postcards were actually mailed out???

We use a direct mailing company for some of our clients, and we always request the company provide to us a postage statement that is issued by the post office. The company you used should be able to request a similar report from the post office that they dropped the postcards at.