Landlord put a Rental LockBox on My Apartment

[Rick Brill]

I rented an apartment in September and paid the FULL years rent up front over 9,000 including security. In January i took a job that kept me gone for months at a time .My landlord put a lockbox on my APT stating he sent me a letter asking if i was still living there ,i didnt respond so he put a real estate lockbox on the apt moved my belongings out and advertised it for lease!!No one seen him move anything out and he claims he didnt.IS IT LEGAL TO DO THIS??