The sum total of what Temple (1922) has to say about Wutana is:
There are 1,075 Wutana in Bauchi Emirate. (p. 367)
and
105. Wutana, population 1,075 in Bauchi Emirate. (p. 431).
On this basis, a hypothetical "Wutana language" was mentioned in early editions of the Ethnologue, but has now been removed. However, it is also alluded to in Roger Blench's draft list (http://www.uni-bayreuth.de/afrikanistik/cnl/gazetteer/list.pdf) of Chadic languages, and in Jouni Maho's list (http://www.african.gu.se/maho/eball/zoney.html) of unclassifiedAfrican languages.
Bibliography
Temple, Olive 1922. Notes on the Tribes, Provinces, Emirates and States of the Northern Provinces of Nigeria. Argus Printing and Publishing Co. Capetown. pp. 367, 431.
Ethnologue: Languages of the World is a web and print publication of SIL International (formerly known as the Summer Institute of Linguistics), a Christian linguistic service organization which studies lesser-known languages primarily to provide the speakers with native language biblical texts.
The Ethnologue contains statistics for 6,912 languages in the 15th edition, released in 2005 (up from 6,809 in the 14th edition, released 2000) and gives the number of speakers, location, dialects, linguistic affiliations, availability of the Bible, etc. It is currently the most comprehensive existing language inventory, along with the Linguasphere Register.
The neutrality of Ethnologue as a scientific institution is sometimes disputed, particularly in areas of language classification associated with the Bible and Abrahamic religion.