The question mark separates the locations with the arguments, thus the
location itself is merely '/'.
If you do not have a location set explicitely for '/', you probably have a
default location block ('location /') which will serve all unmatched
locations, thus resulting in 200.
Maybe the intent
My logs have been inundated with hits at example.com/?anything, though in
the actual logs 'anything' is a very long string of characters.
Log entry:
"GET /?anything HTTP/1.1" 200 581 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64;
Trident/7.0; rv:11.0) like Gecko"
(note there is no location for 'anythi