Answer
(Fatwa: 589/589=M/1429)
You were right to immediately discontinue eating the food when you got the piece of pork in your food. The Almighty Allah will reward you for the same. And if unknowingly you have eaten a bite of Haram, then you should ask forgiveness from Almighty Allah and in future avoid eating such food, especially when you are on the trip to Western Countries, do not eat the meat of animals slaughtered of Jews and Christians. You should avoid eating meat in planes and wherever you have a doubt.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband