In its place is a small double-arrow. Chrome has hidden the TreasuryBox icon inadvertently when resizing the extension toolbar. If you click the double-arrow, you'll see TreasuryBox in a drop-down menu.
To restore the extension toolbar, position your mouse just to the right of the address bar. The cursor will change into a horizontal resize arrow:
Click and drag to the left and the TreasuryBox icon will be restored so it's always visible.