Bug 23391 allows to hide ILL status from search which is part of a performance fix by allowing to remove finished ILL from the big ILL request table. It would be nice if we could allow to search by the hidden status when someone chooses to do so. Not including them in the default search, but allowing for them to be a search criteria.
+1 Currently the only way to find any of those would be to run a report or clear out the syspref.