When a Google Doc is briefly made public, services like LinkedIn can access its metadata — such as title and thumbnail — through standard Open Graph tags. LinkedIn caches this metadata for about a week. Even if the doc is later made private or restricted to a specific Google Workspace, LinkedIn will still show the cached preview. It doesn’t mean LinkedIn has special access or that Google is leaking anything; it’s just a consequence of how caching and metadata scraping work. This behavior is expected and not considered a security issue.
1.Whether the document had never been shared publicly, or if it was at some point before being restricted.
2.Whether LinkedIn showed only the title and a thumbnail, or any part of the document content.
3.Whether your friend is part of a Google Workspace domain (e.g., company/org), or a regular Gmail user.