Hi there,
It’s quite strange that the plugin disappeared without you doing anything to it. If it’s a broken copy of the plugin then the site should return an critical error page when you try to open it and WordPress would automatically send your user’s email a notice about it occurring.
But as you said, if you were able to install GP premium and was able to work with its features for a while then the issue may well be host sided.
If this is the case, I’m afraid this is something we can’t do anything about on our end as this isn’t something the theme or the plugin controls. As David said, your best bet to finding out what happened is to check the server logs.