the Korean Tutor

문자 온 줄 몰랐어 (I didn’t notice that I got a text message) : This expression has the meaning that “이제서야 알았다 (I just noticed late)” rather than “몰랐다 (did not know).”

일상회화 (Korean Conversation)

Just after realizing that you got a message, you can say “문자 온 줄 몰랐어 (I didn’t notice that I got a text message)”. As such, you can say “전화 온 줄 몰랐어 (I didn’t know I got a call)” and “메일 보낸 줄 몰랐어 (I didn’t know you sent me an email)” after noticing that you got an email or a call.  This expression emphasizes the meaning, “이제서야 알았다 (I just noticed late) rather than “몰랐다 (did not know)”.