Accepted into university for MS in CS but rejected by professor for research
If you can get a TA or otherwise afford to go, you might still consider it. You are likely to take around six classes your first year. You might meet several professors that you want to work with and who want to work with you. Plenty of students come to grad school without an advisor lined up and manage to find one during their first year. 

It's unlikely but not impossible that you will work by yourself to complete a publishable paper in CS. Even if your work is purely theoretical, you are likely to need guidance at the very least and other resources in general.