A founder cannot be 'removed' unless it is done by the server's administrator or someone got hold of your password. Assuming that your channel service is ChanServ you will type /cs info #YourChannelName or /msg ChanServ info #YourChannelName and int he notices that follow it will tell you if you are still the founder or not.
See how you go.
If it is still your nick then just try to identify to the channel. Always use Status Window to issue authentication commands. Make sure the Caps Lock is off too.