Whats wrong with my Ford KA?

I purchased a 2012 Ford KA from a dealership 2 weeks ago.

At the weekend I was driving on the highway and my oil light came on (my oil was fine) and then my engine light came on in red.

My engine then cut out and I had to be recovered.

The recovery man didn’t know what was wrong but my engine overheated and my battery needs replacing.

It now drives fine and I have no errors on the dash

I spoke to a garage yesterday and there was error codes when he ran diagnostics but didn’t say what it was. He then checked my coolant (it was low) and added water from a kettle. He cleared the diagnostics and checked again and said it was fine.

I then took it to another garage today and they said because the diagnostics were cleared they can’t help. I have no coolant leak though

Is this normal?! I need to find out quickly as I only have 1 month warranty with the dealership.

Please let me know; the car drives absolutely fine but I am a bit traumatised as this car was bought after I had quite a bad accident and I want to ensure the car is safe