I doubt that is the case, Jennifer.  This may help you to undersand the
different kinds of tests available and the degree of accuracy:

MRI, CT, BAER, and other diagnostic tests.

Advances in medicine have made possible the identification of small
acoustic neuromas, that is those still confined to the internal auditory
canal. After routine auditory tests reveal loss of hearing and speech
discrimination (hearing sound in that ear, but not understanding what is
being said), an auditory brainstem response test (ABR, BAER, or BSER) may be
done. This test provides information on the passage of sound information
along the path from the ear to the brain. The results may indicate a poorly
functioning acoustic nerve. A detailed 'imaging' usually is ordered if there
is an abnormality in the ABR test, which suggests the presence of an
acoustic neuroma.

The CT scan has proven to be a powerful tool in locating acoustic
neuromas. Although small tumors still confined to the internal auditory
canal may not show on the plain CT scan, air or contrast materials
introduced into the body will enhance the image of the tumor.

Magnetic Resonance Imaging (MRI) is a more recently developed diagnostic
test which is very effective in identifying acoustic neuromas. MRI uses
modern computer technology to process the results of passing momentary
harmless magnetic pulses and radio frequency waves through the portion of
the body being studied. The image which is formed clearly defines an
acoustic neuroma if it is present. Gadolinium, a contrast material, is
required to enhance the tumor, making it easier to see. Currently, an MRI
with gadolinium contrast is the preferred study for diagnosing an acoustic
neuroma.

Was your MRI performed with gadolinium contrast?  Ususally they are, if the
purpose is to detect an acoustic neuroma...but you might want to ask your
doctor about this.