To check if your droplet has been removed, go to your control panel –> Projects and see if you have the droplet available there.
If it’s not there, most probably it got deleted due to a long-standing unpaid invoice. If you don’t have a backup, unfortunately, you won’t be able t restore it.
If the droplet is still there, the problem might lay elsewhere. I’ll recommend checking if your domain is still registered and not expired. Additionally, see if the domain actually pings. If it does, is it still from your DigitalOcean droplet? If it’s not, you’ll need to point it to your Droplet. If it pings from your DigitalOcean droplet then it’s something with the Droplet itself.
Having said that, check the mentioned steps above to see where we stand, and then we can continue until the resolution.