We have a RAT!!!!!

I go to my bedroom and hear my roommate screaming in fear. I'm thinking in my head wow she must of seen something crazy on tv or online. She comes running into the bedroom and is like WE HAVE A RAT!!!!! she is like I saw it it was huge, and went on to describe where she saw it and what happened when she screamed. I was scared but I got to say I found the situation amusing. She was scared of rodents like I was scared of spiders lol (not that I'm not also scared of rodents). Anyway she left her phone out in the living room so I had to be the brave soul to get it . Poor thing she is really scared and wants to go home. I keep telling her it is not a rat but a mouse. If we had a rat, we would know long time ago. She does not believe me though. We had two of our schools security officers check it out but they had no luck finding it. Well I hope and pray we can find it and get rid of it.