One dead giveaway is the From property.  Things from Sent Items will be from
one of the configured accounts fot the user.  (There could be inbox items
from the same address, if the user sent mail to himself, but those will be
the exception, not the rule.  To locate these, search for items with the
user's address occurring in both From and To.  With exception of items found
by that search, everything from the user came from Sent Items.)

Based on that assumption, add From as a column to a view of the Deleted
Items folder, and sort on it.  That will make it easy to separate them, then
just select and drag-drop.

-Mark