The army Captain is posted in Jammu and Kashmir and his relatives had earlier alleged that anti-national elements were behind his abduction.
Angry locals on Wednesday torched five bogies of Delhi-bound Mahananda Express in Haathras, injuring 13 people, including a circle officer, in protest against abolition of a nearby railway station.
In a public appeal, the army said Captain Shikhar Deep, posted in Jammu and Kashmir with the 8 Sikh Light Infantry regiment, was travelling by Mahananda Express (15483) from Katihar to Delhi on February 6-7.
The search operation for the officer posted in Jammu and Kashmir is being carried out jointly by the Army, Bihar police, Railway police, National Investigation Agency and the Intelligence Bureau in the Kanpur-Katihar-Delhi section, a defence spokesman said in Jammu on Thursday.