All unsold items saved in My Products disappeared.

That seems strange lovecats. Did you delete them by accident? If so, there is no way to get them back if they are greater than 45 days old that I am aware of. 

If they are less than 45 days old you could see if they are in your standard unsold (not on MP) and reimport them from there. 

lovecats

If you have not used My Products for over 24 hours refresh your browser page, otherwise your search gives you 0 results, and you indeed think it is broken and stuff is missing, as sometimes it will not give you the log in page if always in a tab ready to use, you need to refresh tab to get log in page,

Check all your filters are set correctly, Correct folder etc.

If they are indeed missing possibly deleted, and were listed less than 45 days, you can always import them from your unsold folder as callum as already stated,