Ack codes

Is there a limit to how long Xymon/Hobbit will remember an ackcode? I had a situation this morning where a server, which had a disk test that had been alternating between yellow and red for months (I know, but I'm not in a position to force other adminstrators to be responsible) refuse an acknowledgement because "Cookie 611393 not found, dropping ack". If there is a limit to how long Hobbit will remember an ackcode, does anybody out there know what it is. Do they survive a Hobbit restart?

Thanks, Larry Barber