Generally, an easy thing to do is to hop forwards 6 days, make a new character, and check if there are houses missing from your map. I would do that before/after big jumps. An example: Jump forward a week. If you don't care about maintaining villager relationships, just load, save, and quit. Peek 6 days into the future (using the new character). Anyone gone? Alright, go back a week. Peek 6 days ahead, again. Anyone missing now? Keep jumping forward and back.
Here is one very important thing, though: villagers won't ping you if you haven't spoken to them in a long time. So if you know that someone is moving soon, and you want to stop them, you need to speak to them once, get lectured for being a bad friend, save/quit, reload, and then get them to ping you.
If you want to stay friends with everyone, it might be easier for you to tt day by day instead of hopping around weeks at a time. In that case, you would just do the 6 day peek every 2-3 days you move forward.
