I guess your cat have shrinked it. Just expand it back.

Current Firefox releases place flexible space at the left end and at the right end of the location bar container that you can remove in customize mode. You can place the mouse pointer between the location bar and the search bar in normal mode (i.e. not in customize mode) to get a resize pointer that you can drag left or right to change the relative width of both bars (the total length doesn't change). This only works if the two bars are positioned next to each other (order doesn't matter) with no other elements in between them. If this doesn't work then click <u>Restore Defaults</u> on the Customize palette page. *https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars