The other thing to consider, is just because the other video is under creative commons, THEY might not have had the rights to use some music, and if you're re-using content under creative commons, there might be a copyrighted song they didn't take into consideration, which could lead to a strike unintentionally.
Also, some people who upload content might not actually be aware of what creative commons is and might have uploaded using that setting by mistake. I'm not a lawyer so I can't speak to the legalities of that side of things, but it's another reason as to why they may have striked you, then it's up to you what you want to do.
I think there may be an option to try and contact the creator directly, perhaps you can ask why they gave a strike when they had the video under creative commons and work it out that way. Might be a quicker, cheaper, and more peaceful way to resolve the issue.