Should I remove the invalid citation from reference list?

Hi all. I have really a weird issue with my citations, and I don’t know where can I find an answer to it so here I am posting my question in the hope of getting the right advice. During the research, I found a very useful blog post by the student on a university blog (not mentioning the name of the university) which was a bit controversial. I studied that blog and it was directly addressing one of the independent variables for my research about the student psychology in high school! I cited it about a year ago and now when I was editing my thesis and organizing the citations, I tried to locate those to check if they are available now or not. But see! That post has been removed by the university and now that particular reference has remained invalid. Now I have no idea what should I do! I just don’t want to remove it because then I have to rework on it for which I have lesser time. Please advise.

Posted in: PhD Thesis, Research