The woman obviously didn't know she was missing. She may have also not been paying much attention, as once again, this was a once-in-a-lifetime trip and she might have been busy trying to admire and respect the beauty of nature.
I'm sure you'll be relieved to hear the missing woman was found. I'm sure you won't be surprised to hear the reason she was found was because the missing woman finally realized she was the missing woman and alerted everyone.
It turned out this all occurred because the bus driver hadn't counted the number of passengers properly and gave an incorrect description of the woman to authorities. This was reminiscent of a similar story that occurred in Iceland in 1954, where a young woman joined her own search party after she was reported missing after changing clothes while berry picking.