I just "discovered" that search (note: I talk about search, not replace!) doesn't work for text on locked layers.
Some people suggest to enable "Include Locked Layers and Locked Objects" and "Include Locked Stories" options to workaround this issue, but this solution doesn't work for; neither for Anne-Marie, co-founder and CEO of Creative Publishing Network, creativepro.com, see the discussion here: https://creativepro.com/topic/indesign-cs5-question-finding-a-text-in-locked-text-frame-79/
I use CS6. The issue might have been fixed in newer versions, but I don't really know. Is it so?
And are there any workarounds (except for using GREP instead of normal search)?