Well, this hasn't gone too well. Here is what I received today from CS:
Dear Concerto,
Thank you for your recent correspondence regarding miles for the stay at the Hilton Garden Inn Milan Malpensa from Oct 29, 2018 to Oct 30, 2018 confirmation# xxxx.
Upon further review of your inquiry, per our liaison, we are unable to award the Lufthansa promotional miles due to the Lufthansa airline account was not attached to your reservation and in order to receive the miles the frequent flyer account must have been provided at the time of booking, check in or checked out. Unfortunately the offer is not retroactive for past stays and ended on Oct. 31, 2018. We are terribly sorry for any inconvenience this has caused.
Should you require further assistance, please contact the Hilton Customer Service Center at the address or telephone number listed below. Any Honors Customer Service Representative will be happy to assist you.
Thanks for your ongoing loyalty. If you have any questions, you can connect with us via email, or reach us via telephone at +1-800-446-6677
Sincerest Regards
Hilton Reservations and Customer Care