I work at an insurance company and have been in the industry since the early 80s.
The requirement for a referral waxes and wanes. Right now, insurers are pressuring primary care physicians to set up their practices so that they are ready to become "medical homes" so that they can receive higher reimbursement under Federal Health Care Reform. Also, many insurers and specialists have issues with self-referrals as there is a segment of the population that insists on seeing a neurologist for every headache, and an orthopedist for every joint ache.
I would recommend calling the insurance company and asking if the primary care copay can be waived if the sole purpose of the visit is to obtain a referral. Then, ask what their policy is about the 2nd and subsequent visit to the same specialist. Do they keep the referral open for the duration of your problem, or for a specific length of time?
Also, to avoid having to pay for a second visit, anytime your doctor recommends a specialist, DO NOT LEAVE THE OFFICE, until the doctor has entered the referral in the system!!! Having the right paperwork with the right dates is key.
Getting familiar with your policy is the best way to get what you need when you need it.