for every action there is an equal and opposite reaction; the loco (and the train) thus received the same force by which they impacted the jeep.
Because the jeep itself is heavy, owing to its own inertia it would have given very high amount of reaction force before allowing the mechanical force to dissipate throguh its surface.
This is also the reason why many trains on hitting buffaloes/bulls end up getting delayed; the impact of hitting a 1 ton bull/buffalo usually damages the loco, many a times disabling the brake pipe, for instance...
more... and delaying train by hours.