Stashes are based on commits, not branches. However, the default "title" of a stash—which is actually just its commit message, as each stash is just a commit that's not on any branch1—has the form WIP on branch. So, you can run git stash list, and then use a filter on its output to extract any line containing the branch name. For instance:
git stash list | grep s9feat
(remember that grep searches for any substring, so as long as s9feat is long enough to distinguish the interesting stashes from the uninteresting ones, that's all we need here).
If you've changed the titles of the stashes, of course, this won't work. Since branch names are meaningless and irrelevant to Git, and only appear in the human-oriented message part, you'd need something considerably more complicated to find the interesting stashes—unless, that is, you already put the interesting part into these changed titles.
1Technically, each stash is at least two commits. Stashes made with particular options add a third commit to hold untracked files.