From the menubar, click settings-->"Show toolbar" to get back the tool bar. If you lost menubar also, then rightclick in the kopete window and select "show menubar".
If everything fails, play with the following file: ~/.kde/share/config/kopeterc
Rename that to something else or delete it to reset everything to defaults. In general, if any kde application get messed up, the first place to go and look for is ~/.kde/share/config/ look into the relevent "rc" file. Also ~/.kde/share/apps/
Cheers!