rammus appearing/teleportation out of nowhere

been seeing a loit of rammus lately and now i see why. he was in ball form and just popped on my screen out of nowhere 3 steps from me like he was in stealth. currently in game right this second. his team got multiple kills because of it. I noticed it before in other games as well but thought it might have been my computer. but this time it was right beside me and he killed me because of it. and everyone on my team saw it.