If you are changed skin or mixted some skins, you are lost the "link" with button image. All skins have a toolbars.cfg file that include the toolbars definition for this skin. For example in Phoenity (default skin) this is the definition for searchbar that include the search button you lost;
&Search Buttons{
Search{
%ifplugin macros
# EITHER:
macros(Search)|_Search_Engines
# OR:
# macros(Search)|&Web Search
Type a word or phrase in the URL Bar, then click this button or press Ctrl+G to search the Web. Right-click to choose different search engine.
%else
ID_NAV_SEARCH
Search the Web
%endif
searchhot.bmp[0]
searchcold.bmp[0]
}
# %ifplugin macros
# -
# Forums{
# macros(Search_KMForums)
# Search K-Meleon Forums
# searchhot.bmp[8]
# searchcold.bmp[8]
# }
# %endif
}
Check file name and format (BMP) for the icon/image of button. Number in brakets are index position of image in bmp file when bmp file include more than one image, the first at left is the number 0 (zero).