Google's Safebrowsing Diagnostic page lists "the last time suspicious content was found on this site". But what does "suspicious" mean?
Google's automated malware scanners have been highly accurate with an astonishingly low false-positive rate. Part of that success has been because their definition of "suspicious" actually means "has nasty malware". If the scanners aren't really sure that a site has malware, they won't add it to the malware list. And that's the definition of "suspicious" ("has nasty malware") that Google's Safebrowsing Diagnostic page uses - content bad enough to get a site added to the malware list.
When the scanners do a review of a site to check if it should be removed from the malware list, they use a more stringent definition of "suspicious". If there's any suspicious activity at all then the site will not be removed from the malware list. Often sites have been infected with malware in multiple ways and the scanners need to be sure that it has been thoroughly cleaned up.
Those different definitions of "suspicious" may cause confusion when looking at Google's Safebrowsing Diagnostic page for a site that has been reviewed. The review may have found "suspicious" content that was not "suspicious" enough to have added the site to the malware list - but it is "suspicious" enough to prevent it being removed from the list. Google's Safebrowsing Diagnostic page won't list the date of that review scan.
If you're looking for the status of a malware review, log into Google's Webmaster Tools - the same place you reqested the malware review. It will show whether the review succeeded and will list urls that were still found to be "suspicious".