I have heard back about the type of test that was done.
Typically, the proof that the screening urine test was a false positive is a confirmatory urine test that was negative, which is why knowing the types of urine drug test that was done is critical.
Performing a hair drug test at this point would not prove that the urine test was a false positive. Although hair drug testing will look at drug use over the previous 90 days, the hair drug test will frequently miss single uses of a drug. So, a test for cocaine that is negative does not prove that a positive urine test was false, because the urine drug test could easily detect a single use of a drug, if the urine test is done within a few days of that single use.
Testing for amoxicillin can be done, but also does not prove that the urine test was false. The reports of amoxicillin causing false positive results are based on isolated case reports, which does not prove that the amoxicillin is the cause of the false positive because it could be a coincidence. Studies done on groups of patients did not show that it is a cause of a false positive result, but the studies have been done on a small number of patients, so does not prove that it never can cause a false positive, only that it is not a common cause of a false positive.
This is why it is critical to determine the exact type of urine drug test that was done. If you are unable to get a timely response over the phone, then you may be able to get a faster response by going to the office.