Technically speaking, there is nothing that you could have done to cause a collision between the valves and the pistons. Not on a pushrod engine with a rev limiter. The only ways for this scenario to manifest itself:
[ul][*]Timing chain failure.[*]Camshaft / crankshaft timing chain sprockets failure[*]Camshaft fracture.[*]Numerous valve springs, retention keys or valve stem failure at once.[/ul]You could not have caused anyone of these failure conditions to happen. I have seen this problem on pushrod V8 engines with 240 K Miles but not on the 4.6 L with 44 K Miles.

I am glad you are getting a new engine from LR, you deserve it, irregardless of this internal engine mechanical failure.

They can easily check by removing the valve covers / timing chain cover / compression check.

Keep us posted, very interesting...

 

I guess the valves were bent.

the other option if it is covered is for them to put in a used engine

 

DO NOT let them put in a used engine, if they try throw a tempter tantrum like a 2 year old.
YOU paid for the warrenty, its not your fault they are going to loose their A$$'s on this.