Finding a specific MAC in Cisco IOS can be accomplished via:
This gives a complete table of Port vs. Mac Addr.
If you want to find a specific mac address, lets say 00:11:22:33:44:5e use:
show mac-address-table | include 445e
The output is similar to Unix "grep" command.
For further debugging you can use show interface status and/or show cdp neighbors to see where it connects to.