You can access details about any historic object even if it has been deleted, through an URL of the form
(works for nodes and relations too).
What you cannot do so easily is search for something if you do not know the id ("show me all deleted objects that used to be in this area", "find something that was called Foo Road somewhere in this city"). For such an endeavour, it may be best to download an old planet file from planet.openstreetmap.org and search in there, or if you know that the object vanished on a certain date you could also check that day's diff file.
answered 15 Feb '11, 08:10
If you know exactly where the missing way is but not what it was called or what ID it was, you might be able to use Potlatch's "undelete" function to get the details. In Potlatch 1 it's "advanced, undelete" - deleted ways will show in red and you can click on them to show the way details. Don't unlock the ways unless you actually want to undelete them of course!
answered 15 Feb '11, 19:46