i think maybe that is "왠 일이야?" it means "what are you doing here" you're right and another expression is "무슨일이야?" it is same mean

왜 일인야? is literally translated to something like "What is it?", though depending on the context it can have the meaning of "What are you doing here?' However, the literal way to say "What are you doing here?" would be "여기 뭐하고있어?" (Yeo-ki-mwo-ha-go-iss-eo)

I looked up in the Naver dictionary and discovered that 왠 is a contraction of 어찌 된 (어찌 = how, what; 된 = happened). 일 = work, deal. and you can say it formal like this: 어찌 된 일입니까? thank you for the question and Tonny for the answer - I could learn something new! ))

Correct writing is 웬일이야. Like What happened? As an example, A friend rang up you at the middle of the night, Without notice. Then you can say 웬일이야? I think 무슨일이야 is more Affectionate expression than 웬일이야:)