The way you reproduce this is by dropping your weapon and then holding square as if you were going to hold it in your hands. while you are in the interaction and your hand extends out fully before picking it up you jump to cancel the pickup. then you quickly go to the surrender emote and exit the emote the best and fastest way out of the emote is to press L2 and pick the weapon up as fast as possible you will need a buddy to verify that it's invisible as you can still see it on your screen but others cannot. This also works with clothing.