[GAMEPLAY] Volibear moving slowly for unexpected reason

link of the game if usefull http://matchhistory.euw.leagueoflegends.com/fr/#match-details/EUW1/2669959083/35185878

volibear beacame unable to recall and then had a movement speed highly reduced for 2 minutes ( until the game end) there was like urgot poison all around him on my screen for those 2 minutes ( urgot wasn't around at the time)