True or not, it's conceivable--Snopes.com says it's a true story. Many animals can survive severe injuries, at least for a while--think of badly shot game animals that get up and run away. Their spleens store a large quantity of blood that is available immediately to replace hemorrhaged fluids and fluids displaced by hydrostatic shock. This coyote may have survived and died later from internal injuries after escaping. I could see where it could have been hit in just the right way that the flexible plastic bumper cover would cushion the impact as it went between the cooling vents and into the front of the vehicle--lucky, yes, but conceivable. Humans are, by comparison to most animals, pretty flimsy creatures, yet we dream up ever faster and more dangerous ways to convey ourselves through space and time.
-CC