That circuit uses CMOS gates, which is good to keep current draw minimal since it's battery powered, but their high input impedance make them sensitive to stati

That circuit uses CMOS gates, which is good to keep current draw minimal since it's battery powered, but their high input impedance make them sensitive to static discharges and other electrical noises that in digital appliances are everywhere. There would be some risk of of false positives. If I had to implement such a protection, I would use a switch in series with a micro step relay that uses a couple of NC contacts in series with its coil so it disconnects itself as soon as it's activated, preventing further activations. This way the power requirement to keep its state is zero. Step relays can be really compact; I've used in the past one whose coil was rated only 2V and it was as large and just a bit taller than a 8 pin DIL integrated circuit. There are also step relays containing two different coils, one for activation and one for deactivation, so a single momentary switch in series with the coil can effectively work as non resettable indicator.