same room at university

I studied for my undergraduate degree at Manchester University 1990-93. There were about 10,000 students at Manchester Uni when I was there. A similar number at the Poly and a similar number at UMIST , more at the business school etc. I lived in student accommodation in my first year, a place called Oak House. Many years later I was working in the city. We had summer interns every year and one year an intern said he also went to Manchester Uni. I asked him where he lived, he named the area, thats where I lived, I asked him where in that area, he named the same halls of residence i was in, Oak House. I asked which block, he was in my block. I asked him which flat, he was in my flat. Finally we got down to the room. He had lived in the same room as me. I was very careful not to prompt him and never revealed any information about where I had lived. Nor did anyone else at work know where I had lived so i doubt he had any way to know this in advance. It was a strange coincidence. I would love to know the odds of it happening.