From the question
but this seems like a basic function to me.
Send your feedback directly to Google. This could be done directly from the apps for iPhone. Excuse that I don't give you specific instructions about how to do this in Google Drive and Google Sheets for iPhone. I don't have one with me at this time. This is relevant because Google frecuently change the wording. Usually the path is Menu > Help then you might found an option saying something like "Help {app name} to improve", "Send your feedback", etc.
You might also send your feedback through the corresponding product community https://support.google.com/drive/community for Google Drive and https://support.google.com/docs/community for Google Docs Editors including Google Sheets.
From the question
So it seems like I have no way of actually finding where text is when I have multi-sheet spreadsheet?
Review the iPhone and iPad tab in Find files in Google Drive and the section "Use find and replace in a spreadsheet" in the iPhone and iPad tab
Search and use find and replace. Both links are from Google Product Help, the first from Google Drive Help, the second from Google Docs Editors Help.
Slightly related Is there an iOS spreadsheet app that can do data filters? has an answer including a snapshot of Google Sheets app for iPhone about using filters.
This is about the Google Sheets apps for iOS. It hasn't an answers yet: In-cell carriage returns in Google Spreadsheet iOS app.
Similar recent question from the Google Docs Editor community whitout answers and locked: search inside all sheets within workbook using "Find and replace" on iPhone