hi texasabels.
It's an age out message for the device id cache. if this is the only message you saw, I suspect you got to the controller too late, and this is just part of a deferred cleanup after the user is (long) gone.
If you have a need for longer term monitoring, please consider using syslog.
having said that, is the customer using an Intel 7260ac (I see that it's an Intel OUI) ? If so, please check out the Intel 7260ac thread on the forum, that kind of symptom is seen in some cases.
regards
-jeff