If someone began
Shemoneh Esrei without a
siddur but in the middle of
davening realizes that he needs one (e.g. he forgot what to say next, he needs to check a halacha pertaining to the
tefilla, etc.), he should signal someone to bring the
siddur or
sefer. If he cannot get help, he may walk -- in the middle of
Shemoneh Esrei -- to get the object for himself. If he cannot decide the halacha on his own, he may ask someone else for the answer. Likewise, he may relocate if something that is beyond his control in the area is disturbing his
kavanah.
(
סימן צו, ס"ק ז; ביאורים ומוספים דרשו, 9, 11 ו־13)