Weird. I just looked up the recent transactions I bought at LH.com and it always had the full ticket number in there with the Mastercard. Amex even shows part of the itin. Another way to find it would be to look up the first segment so they have to look for your name with the flight number.

I would dispute it in any case with your credit card company. Often LH.com just takes approval/authorisation but in the end never submits the charge. Make sure with your bank that it actually was submitted before disputing it...