Can my employer throw my personal belongings away?

My supervisor grabbed everything from my cubicle and put a sign that said trash and the cleaning crew threw it away. I noticed several days later (I don't work in the office every day) noticed things were gone, sent an email to al my coworkers and no one responded. Several days later I sent it to management, and only then was when my supervisor replied. I filed a report on the building and for 2 weeks did not hear anything. I went last week and bumped into the janitor and she explained about the trash sign saying she threw these away. Are they allowed to do this? These included personal and sentimental items. I would like to sue my company, since I talked to them after saying I wanted them to hold accountable the person that did this and they did not seem to care.