So you need to physically find a deployed AP that is controlled by a WLC but don't have a physical map...
(You can find this information in the Cisco Wireless LAN Controller Configuration Guide. Reposted here because it's easier than finding it there.)
To enable the controller to send commands to the access point from its CLI, enter this command
debug ap enable your_access_point_name
To cause a specific access point to flash its LEDs for a specified number of seconds, enter this command:
debug ap command "led flash seconds" your_access_point_name
You can enter a value between 1 and 3600 seconds for the seconds parameter.
To disable LED flashing for a specific access point, enter this command:
debug ap command "led flash disable" your_access_point_name
I believe you can still also issue the led flash commands on the local APs but that requires telnetting or SSHing to individual devices.