So I encounter this quite often. For instance I've just had this situation with my reddit profile. I created a profile and submitted several entries. After 2 days (yesterday) my profile with its entries got indexed naturally. On the next day (today) it totally got de-indexed even though no significant changes were made. I have had the same situation with web20 blogs. Some posts (without a link) got naturally indexed and on the next day got deindexed. Is this normal and what could be the reason for this situation?