These sections should help you, make a copy and take them with you. It sounds like the only violation you committed was not having the placard on your rearview mirror, it's a valid violation but is "CS" type.
22511.55. (a) (1) A disabled person or disabled veteran may apply
to the department for the issuance of a distinguishing placard. The
placard may be used in lieu of the special license plate or plates
issued under Section 5007 for parking purposes described in Section
22511.5
when suspended from the rear view mirror or, if there is no
rear view mirror, when displayed on the dashboard of a vehicle. It
is the intent of the Legislature to encourage the use of these
distinguishing placards because they provide law enforcement officers
with a more readily recognizable symbol for distinguishing vehicles
qualified for the parking privilege. The placard shall be the size,
shape, and color determined by the department and shall bear the
International Symbol of Access adopted pursuant to Section 3 of
Public Law 100-641, commonly known as the "wheelchair symbol." The
department shall incorporate instructions for the lawful use of a
placard, and a summary of the penalties for the unlawful use of a
placard, into the identification card issued to the placard owner.
4461. (a) No person may lend any certificate of ownership,
registration card, license plate, special plate, validation tab, or
permit issued to him or her if the person desiring to borrow it would
not be entitled to its use, nor may any person knowingly permit its
use by one not entitled to it.
(b) No person to whom a disabled person placard has been issued
may lend the placard to any other person, nor may any disabled person
knowingly permit the use for parking purposes of the placard or
identification license plate issued pursuant to Section 5007 by one
not entitled to it.
A person to whom a disabled person placard has
been issued may permit another person to use the placard only while
in the presence or reasonable proximity of the disabled person for
the purpose of transporting the disabled person. A violation of this
subdivision is a misdemeanor, punishable by a fine of not less than
two hundred fifty dollars ($250) nor more than one thousand dollars
($1,000), or by imprisonment in the county jail for not more than six
months, or by both that fine and imprisonment.
(c) Except for the purpose of transporting disabled persons as
specified in subdivision (b), no person may display any disabled
person placard that was not issued to him or her or that has been
canceled or revoked pursuant to Section 22511.6. A violation of this
subdivision is a misdemeanor, punishable by a fine of not less than
two hundred fifty dollars ($250) nor more than one thousand dollars
($1,000), or by imprisonment in the county jail for not more than six
months, or by both that fine and imprisonment.
(d) Notwithstanding subdivisions (a), (b), and (c), no person
using a vehicle displaying a special identification license plate
issued to another pursuant to Section 5007 may park in those parking
stalls or spaces designated for disabled persons pursuant to Section
22511.7 or 22511.8,
unless transporting a disabled person. A
violation of this subdivision is a misdemeanor, punishable by a fine
of not less than two hundred fifty dollars ($250) nor more than one
thousand dollars ($1,000), or by imprisonment in the county jail for
not more than six months, or by both that fine and imprisonment.
(e) For the purposes of subdivisions (b) and (c), "disabled
person placard" means a placard issued pursuant to Section 22511.55
or 22511.59.
40226.
An issuing agency may, in lieu of collecting a fine for a
citation for failure to display a disabled placard, charge an
administrative fee not to exceed twenty-five dollars ($25) to process
cancellation of a citation in any case where the individual who
received the citation can show proof that he or she had been issued a
valid placard at the time the citation was received.