The living roblox model

When I was younger I used to make games on ROBLOX with free models sometimes i may have downloaded viruses from them but i deleted those so it can't possibly still be active right?
Well years later I got back on ROBLOX and edited my oldest game but there was this blocky grey player model without a face teleporting in different locations and the game was privated.
there were no players in the leaderboard either which most likely meant that it was an npc i tried to find whatever item caused it but as i did i could not delete it as if it was locked in some way.