Thank you to everyone who responded to my query regarding unclaimed personal items.  Summary of responses on how libraries handle these items:

Keeping track of items:
Retention of items: Libraries retain items anywhere from a week to a year

How libraries dispose of items by type of item:
​Thanks again!​

--
Lynn Bryer Skazalski
Supervising Librarian, MILS, MS
Caroline Kennedy Library
24590 George Street
Dearborn Heights, MI 48127
lskazalski@ci.dearborn-heights.mi.us
313-791-3824