I find it hard to imagine the lug nuts backing off to point of falling off..Even set to 50lbft...I have never, ever seen or heard or had a lug nut coming off if it was properly fitted and torqued to setting..It simply can not happen...I venture to say a couple were lost because they were only perhaps finger tightened and not torqued at all..and/or possibly over looked or missed when you did the wheels..it is easy to do, overlook or miss a lug nut or two that is..Only other thing, the wheels where not correct for the type of lug nut used.
Over torqueing can cause more problems. Like putting too much strain on the hub and this causes brake rotor warpage or distortion, giving to Brake shimmy...And/or the lug nuts themselves get seized on the stud or stripped...