How to recover Switch IP ?

We have 24 port 10/100 Mbps managed Switch. Console port is not working now. Earlier Administrator defined some IP address to this switch which is not known to anyone.
Now as he has quit so we need to recover that IP.
How can I recover the IP of this switch? Someone told me I can use sniffer for this…Will it work…How to use sniffer.

Remember, IP defined on switch is not of our present network range of address…