Firefox has a page called Add-ons that you access by going in the "Tools" Dropdown box. (On my MacBook it's at the top of the screen.)
By bringing up the Add-ons page - a listing of all Add-ons you've chosen - you will see the line with the NoScript Add-on listed. If you then hit "MORE", you >CAN choose to< select to STOP NoScript from continually updating itself, regularly, automatically on Firefox.
I probably wouldn't suggest doing that, as NoScript regularly adds fixes and updates to it's scripts response programing. But I wanted to let you know that it IS possible to select that (stopping the NoScript auto-updating) and not have to change the the overall auto-update status for Firefox, or your computer in general.
You're better off recreating/resurrecting the missing icon/button. I found MY missing NoScript Button on my Addon Bar, which I had UN-enabled (because I had had nothing on it & because the Status Bar seems to work better for me). By going (in Firefox) under the "View" Dropdown you can select "Toolbars" and then select/unselect 'Status Bar' and 'The Addon Bar'
After I found my missing NoScript Button I went to the near-top /right of the Firefox Window/Screen and selected the Open Menu Tool - which is the =three=horizontal=lines=, one atop the other (looking like a FAT partial I-Ching Hexagram). Once that box opens, at the bottom of the box you can select "Customize" - for Customizing Menu & Toolbars. After that's selected you can move around and rearrange icon items on various toolbars. I found my missing NoScript Button on the now visible "Status Bar" (which I had just before re-enabled thru the "View" dropdown) and I MOVED it back to the Status Bar where it had previously been.
You can put the NoScript icon /button, or most anything else, almost ANYWHERE on these Firefox Window toolbars - where-ever you want them. But, be slightly advised that occasionally moving too many things around makes something seem to disappear again. I've had that happen and had to uninstall/delete the relevant Firefox Add-On, and then re-install it, just to get the missing button back. USUALLY, however, moving these little icon/buttons around isn't too much of any problem.