If you can demonstrate to me the existence of even one single type of warm blooded lizard, then your hypothesis might be valid.
Until then, it is just a hypothesis. Comparisons with birds or mice or cockroaches nonwithstanding. And the known facts point towards dinosaurs being cold blooded.
That's begging the question... taking as a given the false premise that Dinosaurs are reptiles.
While not a "lizard," this reptile, the Leatherback Turtle, is indeed a warm-blooded reptile:
"The largest of all living reptiles, the leatherback, Dermochelys coriacea, is an annual visitor and rare nester on the southeastern coast of United States. April and early May seem to be the period of the leatherback migration into Georgia waters. This concentration of turtles coincides with the occurrence of vast numbers of the cannonball jellyfish. The diet of these huge turtles is made up almost entirely of jellyfish.Interestingly, the body temperature of this reptile is warmer than its surroundings. This makes the leatherback the only known "warm blooded" reptile. - Gray's Reef National Marine Sanctuary
Apparently your "known facts" are a bit outdated?
Please read the science that has been developed about dinosaurs over the last 30 years and pay particular attention to the growing fossil samples with feathers... then get back to me on the idea that Dinosaurs are lizards.