If there is a defect in the code but the end user never finds it, is it a bug?

In round-1, Q. Basic questions about API testing, Client server architecture, Security testing, performance testing. In round 2, Q. Mostly same round 1 questions and my current project related questions like roles and responsibilities and my contribution towards release. In round 3, Basic Testing questions. includes functional, non functional, SQL, web testing etc In round 4, Q. Majorly about my project and in details. This round was all about what values I carry, what is my confidence level and honesty. In round 5, HR interview questions-phantom questions. Personal Interview type. Salary expectations and Notice period. In round 6, Offer discussion and Salary breakup discussion