Deposits are rarely lost over big things. They are lost over a list of small ones, written down by somebody standing in an empty room with excellent sightlines and nothing to distract them.
They start where you stopped looking
Inside the oven. Behind where the fridge stood. The inside faces of cabinet doors. The window tracks. The extractor fan cover in the bathroom. Every one of these is invisible while you live there and unmissable once the furniture is gone.
Book the clean before the last day
This is the single most useful thing in this article. A move-out clean scheduled the morning of handover has no slack in it. If the oven turns out to be a job in its own right, you find out at the moment you can least afford to.
One clear day between the clean and the handover turns a crisis into an errand.
Photograph it after, not before
Take dated photographs of the empty, cleaned unit from the doorway of every room. It costs four minutes and it is the only evidence that exists on your side of the conversation.