Was there ever a planet between the orbits of Mars and Jupiter?

The general opinion of astronomers is that material in this part of the solar system would not have had the chance to assemble itself into much of a planet because of the tidal influence of Jupiter. Even if you added up all of the material in the asteroid belt, you would not get more mass than we find in Saturn's little moon Rhea (about 2.3 x 10^24 grams) which is a moon only 1200 km in diameter. So, if a large body existed there, we are not talking about a 'real' planet like Mars or even one of the large satellites of Jupiter like Callisto or Ganymede.

Once upon a time, there were LOTS of bodies a few hundred to a few thousand kilometers across, but they eventually were captured as moons, or crashed into the growing bulks of the existing planets leaving behind large craters, or ejected from the inner solar system by Jupiter and they now reside in the Kuiper Belt. Perhaps in what is now the asteroid belt, two or more of these bodies collided. That would explain the structure of the asteroids and meteorites that we now observe.

We know that asteroids come in 'stony' , 'carbonaceous' and 'iron/nickel' varieties. Also microscopic studies of their crystalline structure shows that many of the asteroids come from 5 - 6 distinct families; perhaps the original five or six bodies collided billions of years ago to form the rubble we now see. Also, the crystals in the meteorites from the asteroid belt are big enough that the rock must have cooled slowly as though it were part of larger bodies once upon a time. There is plenty of evidence that the asteroids were once a smaller number of bodies that collided. But again, these bodies were MUCH smaller than what we now call planets.