First take a few deep breaths...you need to be calm. People listen to you better when you're calm.
It's good you want to help this kitty. Kitties are pretty tough. If he can run away from you, he has some strength left.
Please don't go into an abandoned basement. That's not safe for you, and the cat may well be able to hide from you anyway. This is what it will do if it's scared.
You can call the fire department; you can call the local animal shelter (although I would try the FD first.) Call the NON-emergency number from the phone book. Don't use 911, or they may be too irritated to listen about the cat.
Tell them who you are and where you are and explain the problem. Tell them the address of the house where the cat went. Ask them what they can do. If they can't do anything, ask them who you should call, who can help you. Don't give up.
You have to stay very calm to do this, because people have trouble taking other people (especially kids) seriously if they sound hysterical.
There are plenty of people and organizations who will help stray or abandoned animals. Just stay with it until you get someone who can help.