I have found caches that I could not physically access the log book due to placement+weather. My rule of thumb has been if you can put your hand on the container (and accessing the container isn't part of a puzzle) but you can't remove it from the location due to being frozen in, you have still found the cache and should deserve to log the find. I found one a month ago that was half submerged in ice, with the lid loose. I could see the log book, but would have had to chip about a quart of ice out of the hole to put my hand on the log book (which would have been waterlogged beyond use anyway).
I did another cache this winter that was an ammo box under a log. I loosened the box enough to move it around, but the log was there to stay and the ground was frozen. In order to get the box open, I would have had to do enough damage to the log that the cache wouldn't be hidden anymore.
If I can see the cache (or suspect I know where it is) but there are muggles around, I'll wait, orbit the block or come back another day.
Again, this game is kind of like golf, you aren't playing against others, just a challenge for yourself. If you are in the same county as the cache and decide to log it, you are only cheating yourself. You have to decide in your own mind if you made a "fair" find or not.
Those are my principles. If you don't like them I have others.
~ Groucho Marx