This is probably the only real hope. Problem is you cannot subpoena Google without first filing a lawsuit. So, you'd need to come up with a legal basis to fil

This is probably the only real hope. Problem is you cannot subpoena Google without first filing a lawsuit. So, you'd need to come up with a legal basis to file a lawsuit in which this document would be relevant. And then you'd have to serve a subpoena on Google. You could potential have a lawyer serve a document preservation request on Google before a lawsuit is filed. But I'm not optimistic they'd listen to it.