i lost my mobile phone with all my contact numbers stored in it and need to find a number that is unlisted
I usually search via search engines for the number, News groups too.
Often, if the number is related to a business or charity, it will be there.
If it is a personal number, your best option is to ask the person who has the number directly and specially if it is a mobile number as it makes it harder to find.
Also, a small tip for the future, Synchronize your mobile with your PC, it’s always good to have a backup, I do that once a week and feel a lot safer about my contacts numbers being always up to date.
Hope this helps.