Sounds like your host is having database problems, whether they're owning up to it or not.
Tables don't just "disappear", and content doesn't just "disappear".
The only way Zen Cart lets you delete products is via the admin interface, one at a time (or one whole category at a time by deleting the category).
If all your products have disappeared and individual parts of MySQL engine structural files are disappearing, then your hosting company is clearly having database problems or else is being hacked.
If they won't own up to it and commit to finding out the cause and fixing it, then ... run to another host. You can't run a business on such a host.
Now, maybe they're trying to be helpful and figure things out for you -- that's great. One would have expected them to react by looking at a backup ... but then again if they don't do regular backups of their server I suppose they wouldn't have that option.
If you've made your own backups, you should be able to recover the data. If not, you'll have to start over.






