If you're talking about finding items on the statue, what you are
really wanting to do is break it. Statues are containers that cannot
be opened, they can only be destroyed, at which point their contents
will be dropped on the ground. Shatter the statue with a force bolt
(there are other ways too) and see if any books or items dropped in
addition to the piles of rocks.
Same way you search boulders - Destructive testing.
You can "search" statues with a wand of probing.
This interacts nicely with the bug their weight isn't computed
correctly on special levels. That means you can lug the Oracle statues
in a straight line, probe them, and keep the empty ones as souvenirs.
(Or just force bolt the entire row in one casting, preserving power.)