Blown engine???????

Now ive totally lost all my faith in my Range rover
Just had my blend motors fixed yesterday, all running fine and dandy, TILL.....
Was driving along n heard a loud bang sounded like a flat tyre so pulled over n checked it only to find a loud rattling coming from the engine, like something was loose. ive turned the ignition off and popped the bonnet, to see that the air box has completely come off, so that must of been the bang. Ive gone to tick the car over and it is rattling away but i cant see where from and i have now power at all just idle
Does anyone have a rough diagnosis (expect bad lol), and what my next steps should be
Kind regards
Matt

I see from your profile that your engine is a 4.6,are you running a single point LPG system ? If you are the bang was a backfire and has probably taken out the air flow meter.

Thanks for thr reply
Yes thats right, its a 4.6 with a single point LPG system.
Is it likely theres more damage from that, ie valves, pistons?

Thought so ! The way to find out what other damage is done is to perform a compression test,and to hook the car up to Testbook to see what faults are logged.If the airflow meter has failed the engine should still start,it fires up on defaults and starts to look for an output from the air flow meter at about 500rpm.
Think you need to find a good local independant LR garage that is known for diagnostic work,ordinary garages seem to struggle with them.Might be worth a post to see if anyone will recommend one.

Update
Finally picking my car up after three long weeks without it.
It turned out to be the flex plate that went on the gearbox which damaged the crank sensor
Thanks for everyones help and input
Matt