[Gameplay] Rek'Sai Perma stunned by Pantheon

I don't have a video or screen shot, just my memory. I was playing blue side Rek'sai, and entering my jungle via the route south of gromp. I saw movement and fired my q while underground. Pantheon jumped on my while I was near the 4--way intersection between golems and gromp. I stayed stunned until I was dead, and was never able to unburrow. I tried to auto attack, and hit w. He jumped on me other times whilst I was burrowed, but never had the same result. The only items I had were tier 1 boots, and the completed stalkers blade with warrior enchantement. I don't have anyone with me right now to try and reproduce the bug, hopefully someone out there does, and can.