This happened to me as well. My wand disappeared, (I had been storing it in a chest to save space), the retrieve my tool feature gave me a basic one with no upgrades. I went to the main without saving and opened the day again and my lumina wand was back. But I weirdly now have a random basic wand in a chest on my regular farm that I can't get rid of. I now keep my lumina wand in my inventory at all times to keep this from happening again.
They added in a recent update the ability to go back to previous days. So if you already saved, you can go back to the previous day where your wand should still exist. Open "Settings", you'll be in the default "Game" tab, and scroll to the bottom and switch "Show Backup" to "Yes". Go back to the main menu, click on "Play" and in the bottom left corner should now be the option "Show Backup", click the box, and under each save file will be the previous 10 days, each labeled with the date. I would just go back one day at a time until you have your wand again.
