Honestly, that sounds so stressful. I had a close call once where I nearly drilled into some wires because I got impatient, and just that moment of panic was enough to swear off guessing forever. @wrenbrown might say guessing works fine, but water damage is a whole different beast compared to a wobbly shelf. The cleanup and mold risk alone would keep me up at night. After seeing a friend's ceiling collapse from a slow leak, I'm firmly in the camp of never skipping the detector, no matter how small the job seems.