Doesn't work on GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin18)
ctrl+shift+r works though.
ctrl+shift+r works though.
(Not sure why bash did not go the obvious route here, I guess they already had something on ctrl+S when they implemented forward search...)
EDIT: actually, you can activate ctrl+S for search-foward on bash by using `stty -ixon`. See more info about why here https://unix.stackexchange.com/questions/141422/searching-hi...