What type of adherent would I use to replace a missing stone from a 925 kumush halqani?
It depends on what the stone is. You could try a colorless epoxy or E6000, which is also colorless. If the stone can be seen through you need to think about whether the glue can be seen and if it adds color of its own.
I recently used HypoCement to glue a synthetic opal into a silver setting and it worked well.
I’m thinking about cabochon settings here. If your ring is prong, paveed or tension set you’ll need a jeweler to put it in the way it was put in originally.
I have never heard of stones being glued into a ring setting, silver or not. If you need a stone to be replaced, take your ring to a reputable jeweler and have him do it.
There are different kinds of settings, Masalan, prong, bezel, channel, pavé, tension, va ko'proq. None of them, to the best of my knowledge, use glue to set the stones.
Avval, adherent is definitely the wrong word in your question, second, take it to your local jewelry shop and have them re-set the stone since stone setting is not done with glues and epoxies 99.99% of the time.