they kept daily diaries, if they seen a yeti someone would have wrote about it. This picture is the back shot of one of the hikers walking ahead, you can see his trail thru the snow. The reason he looks taller is because they are standing/walking on 3+ feet of packed snow.

I am not convinced of this. The figure's proportions are too odd, thighs too stubby, arms too long, torso too large. There is no one else in the photo, so who's to say only one of the campers witnessed this animal and took the photo, but didn't mention it to the others for whatever reason. Hence there would be no mention of it in their diaries.

There is actually a satirical mention of Yeti (in general) in writing attributed to the campers, some kind of made up headline written down in jest. So maybe Yeti did come up in conversation, but not this explicit encounter, maybe brought up by the witness who did not want to explicitly say they saw one, and so talk of yeti's turned to humor.