I just got as far as bringing a waterlily leaf home in a plastic bag. I had swirled some water around in the plastic bag and then emptied it like I do for all leaves before I put them in and seal it. The water that clings to the bag keeps them nice and fresh til I get home. I forgot the leaf for a few hours and couldn't think what in the world it was when I noticed it later. It had shrunk to half size and turned black. I threw it out. Sorry I can't be more helpful but I would suggest you transport it in water and cast it immediately if lotus leaves are anything like waterlily leaves.
Laura