Last year, at trail crest I noticed that I had left my tag on my backpack and didn't transfer it to my daypack. I figured that if I was confronted, that the ranger might cut me a break.
And keep in mind they all carry radios, so can call the VC to check whether you have a permit or not. Personally, I would not stop a summit bid on Whitney - or other mountain - if a tag got separated from my pack. I don't recall ever seeing a tag blowing in the wind on Whitney, but have seen several on Mt. St. Helens.
