Pressing the Save For Later button on your daily log-in reward saves the reward for later…
But specifically on the character it was clicked on! I lost my day 2 reward on my engineer because the daily rolled over while I was crafting on him and I didn’t play him again until today, when I got both rewards.
I think this is the type of thing that would be fixed when the log-in reward UI becomes accessible to the players, but since that doesn’t exist yet…