Re: bullet tumbling???????????????
The smallest twig or even lesser masses for a small caliber can easily cause a bullet to loose its stability and 'tumble' them. Were you shooting prone on the ground?
It sounds like this was an isolated insodent, I wouldnt sweat it!
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.