I think this is worth to mention to LH in their customer feedback. We are all very fast when it comes to complaining but normally don't use the customer feedback form to say thank you.
Anyway about the plastic bags. The cheapest way is to buy a pack of 1L Ziplock freezer bags in a supermarket. I know at the airport you don't have the luxury of doing that but I always wonder why people pay for these "special travel plastic bags" when the they are nothng else than normal household freezer bags.