I haven't been able to find the source, however, it may be something I inferred.  For instance, see this block explorer URL.  It indicates that address 12c6DSiU4Rq3P4ZxziKxzrL5LmMBrzjrJX has a public key of 0496b538e853519c726a2c91e61ec11600ae1390813a627c66fb8be7947be63c52da7589379515d 4e0a604f8141781e62294721166bf621e73a82cbf2342c858ee while it says nothing was ever sent from that address.  This blockchain.info URL appears to concur (no sent amount).  Given this, why is the public key there?