Step to recover the accidentally deleted Git Stash:
1. Get the list of unreachable commits, the accidentally deleted commit might still there before garbage collected.
git fsck --unreachable
2. Check through the list of unreachable commits -- <sha>
begin with "unreachable commit", ignore the <sha> begin with "unreachable blob".
git show <sha>
3. Once find the accidentally deleted commit, recover the commit.
git stash apply <sha>