Official comment
Select all.
Right-click.
Relocate.
Find the first file (as shown in the window title) -- don't search for it, navigate to it. If you search for it, you must first use the quick-view.
Select it, and click Open.
It will ask if you want to use the same location for all other missing files, say yes.
Any files not relocated were not moved in the same scope and will need to be relocated separately.