Good luck finding a new DE. Picking up contaminated fuel obviously out of ones control, I'd personally would rather it not happen and could do without the hassle.
A forecourt could say go away and prove the fuel sourced from this station caused the engine fault. Prove that those decats and remap *declared to insurance, plugs that have never been changed weren't the cause of the engine letting go. Does the engine have full vat registered garage service history, helping to indicate it's overall health. Stands a chance a fair few cars on the forum would fail on some of those points alone. Yes we know those wouldn't directly cause an engine to let go, possibly proving it is another thing. Then if the forecourt insist you pay for a fuel sample to be sent off. Independent engineers report on the cause of the engine failure. Yes in long run you'd get an engine rebuild. By a specialist? Maybe, maybe not. Overheating issues afterwards as the cooling system can be a pain to do. Misfire at high rpm as dmf been put on a bolt pattern out? Again I'd rather not have the hassle but everyone's different right.