After fueling up. diesel foam clears-up by the time you grab your receipt at the pump. Sure, it is possible with the engine idling while being fueled, that air bubbles could have been sucked into the system, which I doubt, otherwise, we would here of it on a frequent basis. However, in this case, the car has been driven over 1000 miles since the incident, according to the OP.
The Lift Pump in the tank would have been fully saturated with fuel when installed unless the fuel tank was empty. The unit containing the pump is pushed to the bottom of the tank during the installation process. I've installed several of these pumps. When the engine is first fired-up, there will be some rumbling and rough idle for a few minutes until all the air is out. I generally hold a fast idle until all the air is cleared out... takes less than two minutes.
The engine has Unit Injectors driven by the Cam Shaft. The vehicle in question does not have a High Pressure Pump.
Adding an 8 ounce bottle of ashless 2-cycle oil to 15 gallons of diesel fuel provides about a 240:1 ratio (.00416%) which is nothing compared to a typical 40 or 50:1 ratio for a 2-cycle engine. Thus, other than providing a minute amount of additional lube, it should have no negative affect on engine performance. However, the fuel gelling issue might possibly be negatively affected. But, if the car has been driven 1000 miles and shows rough idle, bad performance, etc., then the gasoline may have damaged the Unit Injectors.
The only other suspect would be as indicated by some of the comments, there was a problem already beginning to show it's ugly face ............. what would it be? Cam lobes for the Unit Injectors sure comes to mind.