Pursuant to Illinois law:
Quote Quoting Illinois Compiled Statutes, Section 820 ILCS 115/5 - Employment Law
Sec. 5. Every employer shall pay the final compensation of separated employees in full, at the time of separation, if possible, but in no case later than the next regularly scheduled payday for such employee. Where such employee requests in writing that his final compensation be paid by check and mailed to him, the employer shall comply with this request.

Unless otherwise provided in a collective bargaining agreement, whenever a contract of employment or employment policy provides for paid vacations, and an employee resigns or is terminated without having taken all vacation time earned in accordance with such contract of employment or employment policy, the monetary equivalent of all earned vacation shall be paid to him or her as part of his or her final compensation at his or her final rate of pay and no employment contract or employment policy shall provide for forfeiture of earned vacation time upon separation.
Additionally,
Quote Quoting Illinois Compiled Statutes, Section 820 ILCS 115/2 - Employment Law
Sec. 2. For all employees, other than separated employees, "wages" shall be defined as any compensation owed an employee by an employer pursuant to an employment contract or agreement between the 2 parties, whether the amount is determined on a time, task, piece, or any other basis of calculation. Payments to separated employees shall be termed "final compensation" and shall be defined as wages, salaries, earned commissions, earned bonuses, and the monetary equivalent of earned vacation and earned holidays, and any other compensation owed the employee by the employer pursuant to an employment contract or agreement between the 2 parties. Where an employer is legally committed through a collective bargaining agreement or otherwise to make contributions to an employee benefit, trust or fund on the basis of a certain amount per hour, day, week or other period of time, the amount due from the employer to such employee benefit, trust, or fund shall be defined as "wage supplements", subject to the wage collection provisions of this Act.

As used in this Act, the term "employer" shall include any individual, partnership, association, corporation, business trust, employment and labor placement agencies where wage payments are made directly or indirectly by the agency or business for work undertaken by employees under hire to a third party pursuant to a contract between the business or agency with the third party, or any person or group of persons acting directly or indirectly in the interest of an employer in relation to an employee, for which one or more persons is gainfully employed.

As used in this Act, the term "employee" shall include any individual permitted to work by an employer in an occupation, but shall not include any individual:

(1) who has been and will continue to be free from control and direction over the performance of his work, both under his contract of service with his employer and in fact; and

(2) who performs work which is either outside the usual course of business or is performed outside all of the places of business of the employer unless the employer is in the business of contracting with third parties for the placement of employees; and

(3) who is in an independently established trade, occupation, profession or business.
Thus, unless you fall into an exception outlined above, it appears that you are entitled to your vacation pay.