I just wanted to add, my father was in the food service business for 25+ years. I have also personally worked in many restaurants for a long time as well. One thing my old man told me long ago is to always thaw meat in cold water
. You run a very high risk of bacteria contamination when you thaw in liquid above 40 degrees. You may have been lucky so far, but you are running the risk to giving yourself and others food born illness. Don't worry about cold water taking too long to thaw frozen meat either, it really doesn't impact thawing time very much at all. When I'm thawing stuff in the sink I usually check every 20-30 minutes and drain and refill the sink with cold water if it feels like it's "too cold".
Thawing on the dashboard is probably fairly safe as long as it's just on the way home and your not stopping for an appointment or running errands all day. Just be safe and always use your better judgment.