I think you nailed it I did see this aircraft when I logged the audio, so I think it's AR-609
For those interested, if you ever want to monitor or confirm who is working in AR609 or Viper the entry/exit to this airspace is controlled by Boston Center on 123.875/323.000 or sometims the low frequencies 135.250/377.100 are used. These VHF frequencies are covered by the LiveATC
ZBW Boston Center (UCA09/ART08) feed.
From the LiveATC archives here are all the ATC comms from that excercise in that sector. Players are KC-135 (57-1456) DECEE 52, with 8 VT ANG F-35s, SHINER 11 (x2), CHEDDER 21 (x2), BIG 31 (x2), THUMPER 41 (x2).
LiveATC Audio
CHEDDER is a new VT ANG callsign for me.