In some of the searches there appears to be pictures missing

example:

http://behoimi.org/post/index?page=5&tags=one_elbow_glove
through to
http://behoimi.org/post/index?page=10&tags=one_elbow_glove

is this because the pictures were removed or is it some sort of error?

There's a set of images in there hidden from public view.

Why are they hidden and how can they be viewed?

Normally, they are hidden because they may not fit community standards on 3dbooru, or in some cases, the model has requested that we remove them from view.

If they're just deleted, why are so many showing up in public searches?