Your Zotero folder would only vanish if you deleted it — e.g., by using some disk cleaning tool. See Locating Missing Zotero Data and provide the info requested there.
You should do the above first, but you'd also have to say more about what you mean regarding Zotero being unable to sync.
Upgrade Storage
You should do the above first, but you'd also have to say more about what you mean regarding Zotero being unable to sync.