Same kind of thing happened to me. Hopped in the semi trusty steed (Disco 1) I pull into a burger joint, the type where they come to your car, and I’m sitting there car off key in the ignition in neutral. I eat my food about to go on my way. Dash lights come on but no beeping. I turn the key all the way and nothing, I couldn’t hear any noise at all. Thought maybe it could be a battery issue, but it couldn’t possibly be. (I have a brand new battery and cleaned the terminals when I put it in) an hour goes by and then it decides to start when the tow truck shows up. Still have no clue what happened.
only difference between me and seemingly every one on this thread is I have the notoriously ****e v8.

 

It sounds electrical, I don’t think your V8 is to blame. Maybe your gear selector wasn’t fully in N or P?