Text formatting changed and photos disappeared

I created a simple new document yesterday and typed in around 30 lines of text, I think all Cambria 12 with around 6 x rectangular images of different sizes interspersed with the text. There were no variations in text format, except possibly for underlining of headings.

When I opened the document this morning, which was created and has remained on the same Windows 10 laptop, the style has changed to “Default Style” and the font to Geneva, which I had never heard of, and almost all of the text is underlined. All the images have disappeared, though there are some gaps with carriage returns where they were.

How can this possibly happen? How can I avoid it in future? I have only been using LibreOffice for a few weeks having switched from MS Office and this is very worrying. NB Document was inadvertently saved as MS Word.

the style has been changed to “standard style” and the font in Geneva, of which I have never heard of, and almost the entire text is underlined.

Use stylesheets and cover your text and headlines with them, and do not use hard formatting.
Example: Select text and double-click the desired style. Before that, delete the direct formatting for the entire text, including the headings (Ctrl + M).

How can this be possible? How can I avoid this in the future?

Save your Writer file as ODT (always).

Only if you have to send someone else something (eg doc), save a copy. See How to open files from MS-Office 2007 or 2010 (.DOCX, .XLSX,…)?.

Because of the pictures, look in the menu Tools>LibreOfficeWriter>View, there in “Show / Pictures and Objects”. There should be a check mark.

Maybe the documentation will help you.

and that is very worrying.

That is only, as long as one does not know, one knows a program like LibreOffice must serve.

I wish you success!