Gayle,
After I made my post, I went back and re-read your post.
I must have missed the part about it was running, then died and was trying to relight.
I'm sure that it is HIGHLY improbable, but that acts like there is water in the gas line that freezes at a low point to block the gas flow and that thaws to allow gas flow when you park in the sun.
Another improbable is that the temperature of the propane tank got down to the boiling point of propane and the propane stopped flowing. That is improbable as the boiling point of propane is -43.6F and I doubt that it got THAT cold in Austin. It only got in the mid 20s here.
Please let me know what the gas guys find out.
Tim