the IRS is most likely not aware, however the the US Treasury is fully aware.  I’ve seen US War Bonds that only have a name on the bond (no ssn).  E bonds from 60s and 70s have name, address and SSN of primary bond holder.   US treasury has all this information in their “dungeon” as can be verified when a lost bond claim is submitted.    When US treasury bonds are redeemed, US treasury lumps all interest on the 1099 for year deemed.   Unless the US treasury communicates extra information, which is unlikely, IRS only sees 1099-INT reported for year redeemed.