I am curious, if you havent had this happen since you were 12 and are 32 now, why worry about it?
I really dont think there is a way to know what it was since you weren't wearing a monitor at the time... It could have been either or neither even.
I read your other posts along with this one, and you seem to be wrapped pretty tight, my friend. I think what you're experiencing is pretty much benign considering your overall health and that fact that you have not reported any adverse cardiac conditions, and no prior cardiac surgery. I too have experienced these short 8 ro 12 beat runs of elevated pulse. I had 54 years of SVT before having it fixed, so I suspect its SVT conducting over the ablated area. But like the previous poster said, whatever it is hasn't killed me, so I pause and "listen" to it, and when it terminates, I go in with whatever I was doing. I think you should take what your cardiologists say and stop worrying about this.