I have found other runners by looking for running routes. Sometimes individuals post routes, other times it's an organisation such as a running club or event organisers. These groups will often leave contact details so I have been known to follow those up.
There is the UKA in this country which lists all affiliated clubs. Also a number of websites - this one for example, I think others go by the name of running or jogging buddies - haven't really prooved as useful as here. Just by posting on this site I have found quite a few runners who live, work or run near where I do.
One week, no it will not greatly increase your risk of injury. If you are used to running 30 miles a week and have been doing so for some weeks or months then an increase of 15% is not excessive.
If you do run this week at an increased mileage then make sure that the following week is a recovery week, as you normally would plan for any race or event in which you take part. If you view the week as an event say and plan well then you should be fine and enjoy your time off.