One rule Josh and I laid down in the first plotting session was that Geist had this limit: He had to turn solid to touch something, and he had to touch something to take it into his ghostly field. In other words, he can't just stick his hand through the wall and rip out the alarm, because he'd have to phase into reality to grab it, and then his arm occupying the same space as the sheetrock. He could, if he wanted, extend his field enough to turn whatever he was touching ghostly, so he could push a steel wall in by detaching it from the surrounding material.
Remember that I said that in a few weeks.
So don't think we forgot that in these panels. That's Geist creeping around the corner of the alcove behind Brother Jon in panel 1, and then extracting the pistol in panel 2. In between, he was floating solid and vulnerable behind Jon for the merest wink of an eye. That's all the contact he needs.
Batman would have heard him breathing, detected the temperature change and realized his holster was lighter. I'm just saying.