Here's one way: for all branches not checked out, show the differences between it and the current branch, specifically looking for files which contain the word "poll". For each branch, "trace" (echo) the command first, before listing the files different from current branch.
$ git branch | egrep -v '\*' | xargs -t -n1 git diff --stat | egrep poll
git diff --stat feature/ent958
eimport/epollmail.py | 244 ++
eimport/tests/test_epollmail.py | 149 ++
scripts/epollmail | 18 +
Ah -- my stuff was found in branch ent958. Thanks, command line!