@ellane@obsidianmd I just had some trouble with iCloud today. One of my pdf files inside my vault disappeared from the Obsidian view. I thought it had been deleted. Only to find that iCloud removed the file from the vault probably because it wasn't accessed lately and was bigger than some threshold (I am just guessing here). After I clicked an icon with a cloud with a down arrow inside that the file materialized again.
I do not use Obsidian Sync though, only iCloud sync.