Lump is Just Gone?

I had a fibroademona removed about 6 years ago (38 now). At the time my breast surgeon (since retired) said I have "lump, bumpy breasts" I'm not sure what that means exactly (fibrocystic breasts???) but I also have dense breast tissue. She told me if I found another lump to wait until my next cycle and if it's still there, give them a call. My cycles are all over the place so, what does that mean? Fast forward to July 1st, I woke up with a painful lump on my left breast. I had just done my monthly exams the night before and was shocked to find something so painful. I ended up at my OBGYNs office that day (apparently I'm no longer considered a patient at my breast surgeons). The NP thought it was another fibroadenoma (smooth, round, moveable, feels like a clam -- her words...) but so painful. My first fibroadenoma was never painful. Scheduled an ultrasound/mammogram for a month later. Fast forward 4 days and it is gone. Like gone gone. No pain, no lump. No nothing. Everything back to normal. Then the next day, my period comes. My mom has a history of lots of breasts cysts that started in her 30s/40s and said it sound exactly like that.

Now I feel stupid for going to the doctor (I really only called because since I don't have a regular cycle, didn't know how long I should wait). I still have the scan scheduled for a few weeks from now but I don't know what to think of what happened. Should I cancel my scan since it's considered a "diagnostic mammogram" and there isn't anything there anymore? Should I be worried that it's gone!?! What the heck just happened!