I have done similar, flew domestic into JFK, checked in a few extra boxes there, landed in TLV, checked in, drove home and left some boxes, turned right back to the airport and just made the flights on to SVO.
On the plane at the gate in JFK waiting to leave, they called me on loudspeaker and asked me to come forward with docs. I was very concerned that they realized how many total pcs I had. Some security guys marched me down stairs to the tarmac under the nose of the plane and asked me to confirm that those boxes were mine. I did and that was all.