If the listing is current and indexed, you can search by item number by entering the number directly into the search bar.
If you are using a browser, you can open an item using a link like this:
https://www.ebay.com/itm/234695653990
Just paste your own item number of those digits at the end of the page address. That will work even if the listing has ended within ninety days or if it is not yet indexed.
In the app, you should be able to switch between the new message format and the classic format by using the links in the upper right of the message inbox. "Classic view" will take you from "new" to "classic". "Try it now" will take you from "classic" to "new". Neither of those should affect the messages you see in your inbox, though I do not think the "new" format is set up to handle folders yet, so you may have to switch back to see messages in your folders.
