Stop people overwriting formulas in a shared sheet
It is almost never malice. Someone sorts, pastes a block from another file, or types a number where a formula sat, and the total silently stops updating.
Make locked cells visible
Give formula cells one fill colour and say so in the header row ("yellow = calculated, don't type here"). This alone cuts most accidents.
Add a warning
Warning-only protection (Data > Protect sheets and ranges > Show a warning) makes people stop and think before they paste.
Recover fast
File > Version history lets you restore a whole file, but that also rolls back everyone's good edits. To bring back one cell, open version history, find the old formula and paste it back.
Automate it
FormulaLock does all three in one click and puts locked formulas back automatically, with a log of what was restored and when.
Honest note: restore-on-edit only catches edits typed or pasted in the Sheets interface. Imports, other scripts and API writes are not caught. Full limits.