I am from a city which has multiple post-secondary schools. In high school, I took private music lessons with a music teacher, who had a studio at a local college (but was not part of their actual music school or faculty- this gets kind of confusing). When I started university, I continued to take music lessons with this instructor even though I was a student at the other school. At the beginning of the year, he asked me if I wanted credit for my lessons that would transfer directly to my university degree from the college. It was never my intention to study music at the post-secondary level, but I figured I didn't have anything to lose and said sure. I didn't do any research into this, because I trusted him and didn't think of how this could potentially be an issue (as an aside: I was 17 at the time and probably too young to have started university, I didn't make the best decisions back then). I was given a student ID number for this other college (which I have long since lost), but was told it didn't matter because I wasn't actually their student, I was a student of the teacher's. It was simply a formality.
Over the course of a year, I took the equivalent of two courses from him (one a semester), and received two grades. When I emailed him to ask when they would be transferred, I was told that I would need to contact both the college's registrar and my university's registrar, and that the program that allowed me to take those courses for credit had ended. However, I read something soon after that my university does not allow you to take courses from other institutions without their prior permission. I panicked pretty hard thinking that I might be in serious trouble if I told them about it and decided not to have the courses transferred. After a while, I kind of just forgot about it and went on through the rest of my degree without any issue. I still don't know if this actually would have been an issue for them or not, but I never told my university about those lessons, nor have I had any contact from the college or my teacher.
So, anyways, now it's years later and I am applying for grad schools. All of the schools I am applying to require me to send all transcripts of every institution I've ever attended, but only require me to state my degree-granting institution on the application itself. I'm pretty certain that I must have a transcript from this college, since I was given two grades and offered credit. But then again, maybe I don't, since this instructor wasn't actually part of the college. If I do, I have no idea how I would even request those transcripts. I'm worried about what the consequences of sending/ not sending would be. On one hand, not sending a transcript is obviously pretty bad, but on the other I'm worried about how this would appear to schools if I sent it. Would they be worried about the fact I have classes that weren't a part of my degree, and that I potentially wasn't allowed to even take? How would I explain this if they ask? One of the programs I'm applying to is at my undergrad school, so that's a concern as well. The music lessons/courses aren't in any way related to my undergrad degree or graduate program, and as I recall he gave me an A- both times, so it's not like I'm trying to hiding poor grades or an important class.
What do you guys think? Should I send or not send these transcripts? (if they even exist). Will I have a problem either way, or am I way overthinking this? I feel like I've really messed up by not getting this entirely sorted out five years ago. I'd really appreciate any and all advice you can give.