See, the 'keep you posted when can thing' does imply that the communication may have been blotchy at times even if it was daily
Plus, assuming the environment is full of mountains I really cannot imagine cellular signal would be too good, especially in snowy conditions
I imagine he may have been concerned, but if he did not know her route that well and it was totally possible that she was fine the next bet is to wait for her to show up as planned?
Also, if they travel frequently there is that to add to the context. If I go missing it's a lot more concerning than someone who should have some experience with this sort of stuff