Alt+F4 in the websearch plugin or in verve-plugin makes the panel disappear... it is still running but it is not shown on the screen anymore. You can bring back 'something' of the panel by running e.g. /usr/libexec/xfce4/panel-plugins/xfce4-verve-plugin (if you have xfce4 in /usr) but it doesn't really resemble a panel. Restarting Xfce does not fix it (so please make a backup of your .config before you try this ;) ) gr,S.
Oops ;-) I hope it's as simple as handling the delete signal on the panel window... Thanks for the report.
Should be fixed in revision 22645. Please reopen if it isn't.