Unless the rocket hit near the ambulance and shrapnel caused the damage. I imagine that during a rocket attack people are distracted and might not get the details exactly right. Do we have any data on how long it takes a steel panel to rust after it's been pieced by red hot metal?
A better question is, what difference does it make if the Israelis hit an ambulance with a rocket or not? When a rocket is fired at an urban area, it's going to hit something. A ambulance is as likely a target as any other vehicle.
You couched this proposition as if the Israelis would not fire a rocket at an ambulance, if they could help it. I've never seen any indication from either side of this conflict that there is some kind of concept of a "fair target."
A picture a day or two after the incident wouldn't show rust.
Besides, there's the big problem of what became of the missile. It supposedly punched straight down through the ambulance. Such weapons are generally traveling something like the speed of sound. Taking the mass of a typical air-launched anti-tank missile and it's speed and you get an energy similar to the ambulance hitting a brick wall at high freeway speeds. All that energy did basically nothing to the rest of the ambulance? It supposedly amputated a leg on the way down---but the splash of all that energy hitting the ground did nothing?? (Not to mention that a traumatic amputation like that is a case where survival would be unlikely.)
Not to mention the hole bulged
out, not in--not what you would expect from something slamming through and if the warhead detonated why do we have an intact ambulance?
Occam's razor--it's a pure fabrication.