I lost 9 sites last month - most of them have a last cache date around the same time as yours. All the sites I lost could be deemed to be 'thin' affiliate sites. Just making use out of datafeeds and no/not much unique content. 2 of them were my main bread winning sites that are totally unique. I
am majorly disappointed at them dissappearing from the index.
I have submitted a reinclution request as well. I think that my major sites may have gone because of the overuse of 'backfill' from search results tripping over the duplicate content filter. I have removed these offending results and
am hoping that they will reindex the site soon.
I hope your reinclution request goes well - let us know, as will I