rengar heartbeat bug

i was playing rengar so i tried to 1v1 their thresh but then 3 more people came out an killed me so at the last second i pressed r and then i died.... but then idk if this is a bug or what but i died before i could stealth but my screen still went dark so i was technically stealthed so i think thats also a glitch but then i could still hear the heartbeat of the enemies around me and my team.