A document was uploaded to Ephorus, but no results were found. What happened? 

Of course, it may well be that the document is original and there are no similarities to be found. Assuming that there are similarities, it may be the case that the document does not contain any text that can be scanned (i.e. only images or scans), or that the content is taken from sources Ephorus cannot access (i.e. sources that are not publicly available).