Have you tried calling RQA? If not, their number is: (630) 512-0011. When someone answers, ask to please speak with someone from your project you are concerned about and let them know you have not received the check that was mailed 8/5.
CAVEAT: If you have not done so, make sure the website says the check was actually mailed on the 5th, and not just approved on the 5th. If approved on the 5th, it won't go out for a couple more weeks.