I'm not licensed to practice law in the state of Texas, but:
http://tlo2.tlc.state.tx.us/statutes/tn.toc.htm§ 502.404. OPERATION OF VEHICLE WITHOUT LICENSE PLATE OR
REGISTRATION INSIGNIA. (a) A person commits an offense if the
person operates on a public highway during a registration period a
passenger car or commercial motor vehicle that does not display two
license plates, at the front and rear of the vehicle, that have
been:
(1) assigned by the department for the period; or
(2) validated by a registration insignia issued by the
department that establishes that the vehicle is registered for the
period.
§ 502.409. WRONG, FICTITIOUS, ALTERED, OR OBSCURED
LICENSE PLATE. (a) A person commits an offense if the person
attaches to or displays on a motor vehicle a number plate or
registration insignia that:
[. . .]
(7) has a coating, covering, or protective material
that:
(A) distorts angular visibility or
detectability; or
(B) alters or obscures the letters or numbers on
the plate, the color of the plate, or another original design
feature of the plate.
So, keeping in mind that I'm not a Texas lawyer and I don't practice traffic law, it would seem you could make an argument that your license plate was on the front of the car, so you were in compliance with the letter of the law. But in traffic court, I would guess the default rule is to uphold tickets. I hope this is some help.