Instead of trying to look for the record locator, whatever happened to common sense?
Call LH/LX res.
Give your flight number, date of travel, destination, and your last name, followed by first. All agents can access your booking based on those information. Some airlines might ask for your booking airlines' PNR to verify its you before they do seats and meal selections! And you can then ask what the LH or LX PNR numbers are too!
Total time to do this? Probably 10x faster than for you to ask question on thread and wait for an answer!