Unknown bug hack

i recently played a crossfire game and noticed that nobody saw me. lemme describe this bug.
when the screen was loading when i pressed played i noticed the "disconnected sign"
but after that i wasnt so in the game i couldnt use my shovel when i clicked i heard a beep every time but i could use my primary. so basically nobody could see me but i could still kill them? and when i killed them it showed that they suicided.





someone please tell me what bug is this