I've lost one Moon! How could that happen?

Hey everyone,

Just as the title says. This morning I had 584 moons (not a lot, I know, but still, that's how many I had.) And now, I have 583 moons. I've gained moons before, but never lost moons before.

I have a few questions, and no answers - here they are, in no particular order:

1. Is this a new thing? If so, is there an explanation post somewhere that someone can post a link to please.
2. How could it have happened? I haven't tipped anyone (sorry!) so I know that I haven't 'lost' a moon that way (not that that would count as a loss anyway).
3. Has there been a correction, a re-calculation perhaps? I know that it's Moon Week.
4. Has this happened to anyone else? If so, what was your loss - also 1 moon, or more?
5. Will it happen again? (This is perhaps the most important question that I have right now!)
6. Is there any way to prevent it from happening again?

Looking forward to all of your speculation, theories, and, hopefully, genuine answers. This isn't a joke thread, this is genuine.

Thanks!

EDIT: Thanks to /u/Classroom_Strict/ for getting me to check my vault. Apparently, sometimes mobile and desktop don't display the same. I'd been looking at my mobile previously, and seeing 584, but when I posted this, I was on desktop. I don't know WHY it does that, but I have been assured that once Moons are in your Vault, they can't come out, unless you authorise it. Thank you everyone, I feel much better now!