Damien will give 1 random location out of 5 Mafia locations. You have to visit him at least 5 times for 5 days to find all the locations. Sometimes he will repeat location you already know so you have to visit him again until you get all 5 locations. After you get 5 locations, then you can visit all those locations during night to look for Patrick.
The good thing is Patrick will show up at one location all the time until you can find him. So the idea is to figure out what the first location out of 5 locations. It's actually very close to Damien around the area.