Notes disappear

writing my first notes in obsidian. One of them – the longest one :(( – simply is not there anymore.

because of this I also noticed that I can’t find how to search inside a new vault. In obsidian default vault (obsidian help) there’s a lens where I can click to search a word. But in the new vault, I can only search inside a note. Is this true?

You can try to use the windows explorer to find the file.
Windows search function also OK.

You need to enable the search function: