But the tag was deleted for some reason.
My mistake was that the tag I should have used was soundmanager2.
But that wouldn't be a reason to delete it, but rather change it.
Or am I missing something?
Given that your question was specifically about soundmanager 2, and that there are at least 30 other questions with the soundmanager2 tag, the edit should have been to remove the soundmanager tag and add the soundmanager2 tag.
Note that tags for version-specific questions are not always appropriate; if the question applies across versions, then it's better to tag with the version-agnostic version of the tag. If the question applies to a specific-version, then it's better to tag with the specific version tag and possibly the version-neutral tag.
This is a judgement call, since there's no soundmanager tag, you should really ask "do I need to create one?". Asking this question is usually a good indicator that you don't have to create a new tag (but not always).