We ran into a similar scenario where someone joined without a mic. We asked "dude, if you can hear us, wave." He waved to confirm he could in fact hear us. We asked him if he knew where to place his Titan bubble, he responded with a wave. Fast forward to second sword. We were running out the door towards center when a high pitched voice came on frantically "I don't have my bubble!" Simple and succinct. Most of our group was taken by surprise and even said "what the blam was that?" I calmly said "thanks [squeeker] for the heads up. Other Titan can place his." No one panic. We made it to the ogre room easily and I had to tell him thanks again and that if there was anytime to put a headset on - that was it. We continued to beat Crota easily. Some squeekers aren't so bad.