First job: should I put this on my resume?

Just put it down if you did it, besides they must have considered you worthy of vice captain if they came up and asked you to do it. The same thing is similar for me, we had this officer team who planned socials at my school and a sectional representative who worked on sectional socials and no one ran so they asked me to do it, but because I was the most qualified to do the job. So just because you didn't run or anything doesn't mean you weren't the best for that position.