FLASH BUG, i think?...

So i was in a game playing as mid lane against a mid lane, when he used his E, i flashed, but i misplaced my mouse and by accident right in front of me so i was still inside of E. after doing this his E was still up and i kept running and it just let me run threw his wall without getting rooted. even the asked me what the hell happened, we both had no idea, and were unable to test this again seeing as the game ended. would really like to know if this has happened to anyone else and if this is a consistent thing or if it was just weird connection thing that made me able to do this, but if its a bug, it needs to go because that's pretty game changing.