Partly to bump up this thread, and also to answer some of the points raised above:

I think the guy knows who Mourinho is, of course I could be wrong. He said he was Slovenian and I would think any European football fan, and indeed almost every football fan in the world, would know who he is. There are maybe 5 more famous people in all of football than this attention loving, PR manipulating, media magnet - that's why Nordeus pay him for his face on the product

Most likely, the OP thought that it was a normal user playing under a pseudonym - there was no in-game announcement that Mourinho would appear as a friend, and I only figured out what had happened because you couldn't bid for his players, view his standings, or play a friendly