The DHCP client list only lists the devices which requested an IP address from the DHCP server on the router. Any device which has a static IP address will never appear in that list.
The router usually also has a list of active wireless clients. This list shows all clients which are connected wireless to the router regardless whether they use DHCP or not. Try to access this URL: http://192.168.1.1/WL_ActiveTable.asp The URL should work on some firmware versions but probably not on all. If it does not work, try this:
Go to http://192.168.1.1/ Click tab Wireless. Click subtab MAC Address Filter.
If the wireless mac filter is not enabled. Select the "Enable" radio box. The moment you click on enable you should see a few more choices on the page plus a button to edit the filter list. Click the button to edit the filter list.
A new window should appear showing you the current filter list. The window should have a button to open the Wireless MAC Client List. Click that button and you see the list of active wireless clients.
Once you are done simply close all windows. That way you don't change any settings on the router.