Try telling that to my plumbing jobs, where a three hour bug is just a Tuesday.

Cotton balls snagging is a good trick but it's still a barrier. You're adding a layer between your sense of touch and the glass. That's the whole point. Feeling the surface directly with your skin picks up the slightest texture change a cotton fiber would glide right over. The risk is real but so is missing a hairline fracture. You learn to handle edges with a light touch, not a grip. It's a skill, not just being reckless.

Got to disagree with the idea that checking behind the wall is the main takeaway here. The real issue was mounting a sensor right where an HVAC duct runs, that's just asking for trouble. You should always know where the mechanicals are before you drill, finished space or not. A stud finder with AC detection is basic gear for a reason. This feels like a planning problem, not a weird hidden trigger.

My local garage does that with a $25 fee, and it feels fair.

Ugh, melted plastic crust sounds like a nightmare. Did you have to use any special cleaner after scraping, or just a lot of elbow grease?