WordPress review
If a page loses a sentence during an edit, I’d look at its WordPress revisions before trying to remember the old wording. The history lets me see which version had it and decide how much of that version I want back.
Find the edit that changed the page
Open the post or page settings and look for Revisions. The visual view introduced in WordPress 7.0 lets you select a saved version and show changes on the page. The classic revisions screen compares the HTML side by side. I’d check the revision just before the sentence disappeared and read the paragraph around it before bringing anything back.
Bring back the part you need
If the rest of the latest edit is good, I’d copy the missing sentence into the current draft. The Restore button is there when the earlier version is the one I want. The history can include an autosave, which WordPress labels separately from a regular revision. Ulysses gives me a place to keep a writing draft before sending it to WordPress. The WordPress history is where I’d look for changes made after that handoff.
Anabel’s take
I’d keep the current editor open while I compare the revisions. Once I’ve found the missing wording, I’d preview the page before saving the edit, especially if it sits next to a button or a link that changed at the same time.