As far as I know we never had a block submitted that didn't show in stats, in all 6 years of operation. When block data is submitted it is very carefully taken care of by the pool.

I don't think those stats are accurate. On average it takes over 7 years to find a single block with 13 TH/s. You'd have to be very lucky to find 3 blocks in 4 days.

What exactly are the stats showing? Do you have the hashes of the blocks?