ACR MLG ALT DEVIATION FAILED TO MAKE CROSSING RESTRICTION.

Narrative

ON THE FLL 292 DEG R; WHILE FLYING AT FL190; INBND TO FLL ARPT; I INFORMED THE F/O THAT I WAS TEMPORARILY LEAVING THE FREQ TO SPEAK OVER THE PA TO THE PAX. DURING THAT 1 MIN OF TIME IN WHICH I WAS NOT MONITORING CENTER (THOUGH THE F/O WAS) THEY ASSIGNED US A XING ALT RESTRICTION; WHICH HE ACKNOWLEDGED TO 'CROSS 50 MI NW OF FLL AT AND MAINTAIN 8000'.' WHEN I RETURNED TO MONITORING CENTER AND NOTIFIED THE F/O THAT I WAS BACK; HE DID NOT MENTION THE DSCNT CLRNC; NOR DID HE SAY ANYTHING AS I GOT EVER CLOSER TO THE 50 MI FIX ON WHICH IT WAS PREDICATED. AS I PASSED THE FIX; STILL LEVEL AT FL190; AND STILL UNAWARE OF THE CLRNC; CENTER ASKED US WHAT OUR ALT WAS. WE CONFIRMED FL190; WHEREUPON CENTER TOLD US TO DO A 360 DEG TURN AND DSND TO 8000'. NOTHING MORE WAS SAID BY THE CTLR ABOUT OUR FAILURE TO MAKE THE ASSIGNED XING RESTRICTION; AND WE WERE SEQUENCED IN WITH APPARENTLY NO CONFLICT OTHER THAN THE 360 DEG TURN REQUIRED TO DSND. THE LESSON IS PRETTY STRAIGHT FORWARD: DON'T RELY ON THE GUY YOU LEAVE MONITORING ATC TO INFORM YOU OF CHANGES WHILE YOU'RE OFF THE AIR. EITHER MONITOR BOTH CHANNELS WHILE YOU SPEAK ON THE P/A OR AT LEAST ASK SPECIFICALLY EACH TIME YOU RETURN: 'ANY CHANGES?' ALSO; SEE F/O'S REMARKS FOR FURTHER SPECULATION; WHICH I AGREE WITH. SUPPLEMENTAL INFO FROM ACN 99566: I DID NOT INFORM HIM OF THE CLRNC. THERE SEEMS TO BE NO SCHEDULED REST IN THE COURSE OF ANY GIVEN DUTY DAY; SUFFICIENT TO REALLY LEAVE THE ACFT; SIT DOWN AND EAT A MEAL. FATIGUE IS AN UNEQUIVOCAL CONSEQUENCE.