An engine needs three things to run, mechanical integrity (which it must have or it would not restart), fuel and spark. Intermittent problems are sometimes a nightmare to find. To find an intermittent problem like this if it were happening more frequently I would "tee into" the fuel line and tape a fuel pressure gauge to the windscreen so I can monitor fuel pressure when the problem occurs, if fuel pressure falls off you then start tracing the fuel pump, fuel pump relay and sensors that allow fuel operation.
Your car has good on board diagnostic capabilities, a scan tool connected to the 16 pin socket under the dash should hold information vital to determining what is wrong.
I am the shop foreman where I work and frequently drive customer's cars home at night or at lunch with a scan tool connected, if the car fails to start I can monitor sensor activity immediately. But I see a lot of fellows ust not interested in finding intermittent problems.