IMPORTANT business documents * and your lease would certainly qualify * should be kept in a safe deposit box or OFF SITE of your office for security purposes.
That said, contact your landlord, pay the $$$ you are behind, get BACK into your office and get your copy of your lease and THEN go see your attorney.
I'm curious why you have not called a locksmith and REKEYED the locks to get back in....that would be my first action.
CPM * 45 years of property management experience * Age and experience ALWAYS trumps youth and enthusiasm