The jocular Australian-English phrase gone on the padre’s bike and its variants are used to reply to any request for somebody’s whereabouts.

This phrase originated in the slang of the Australian armed forces during the Second World War, the noun padre being a colloquial military designation of a male chaplain in the armed services.

The text containing the earliest occurrence of the phrase gone on the padre’s bike that I have found indicates that it originally meant absent without leave, i.e. away from a post, place of work, etc., without authorisation—this is the text, from the Daily Telegraph (Sydney, New South Wales) of Tuesday 15^th February 1944:

Troops Call Lady Blarney “Sarge”

Melbourne, Monday.—Lady Blarney, wife of the Allied Land Commander in the South-west Pacific, is called “Sarge” by servicemen in the north.
Lady Blarney revealed this in Melbourne today in an interview on her work as Red Cross representative at an Australian General Hospital in Northern Australia.
“The boys call me ‘Sarge,’ because of my three red stripes as commandant,” she said.
Lady Blarney explained that “gone through” was the Service language for “absent without leave.”
“But this is being supplanted by ‘Gone on the padre’s bike,’” she added.

The second-earliest occurrence of the phrase gone on the padre’s bike that I have found is from Troppo-Easers, by “’Alf ’Itch”, of the RAAF (Royal Australian Air Force), published in the A.I.F. ¹ section of Smith’s Weekly (Sydney, New South Wales) of Saturday 10^th March 1945:

Camp is quiet. Day workers are busy rolling drums, chopping firewood, cleaning incinerators, and generally “holding the bulge.” Night shift chaps are “spine-bashing.” Sun beams down on the lush kunai and palms.
Suddenly the air is rent by the orderly room shiny’s booming voice. We hear him clearly though our tent is 200 yards away in the bush:
“LAC Blank, you’re wanted immediately!”
Instantly there is a chorus. Voices in every pitch and tone reply from the camp environs:
“He’s gone for the milk,” “Pull yer ’ead in,” “Gone through on the padre’s bike,” “Up at the corner shop,” or “Went mad and they shot ’im.”

¹ A.I.F. is the abbreviation of Australian Imperial Force.

The following indicates that civilians rapidly adopted gone on the Padre’s bike, as well as other phrases that originated in the slang of the armed forces—it is from the A.I.F. section of Smith’s Weekly (Sydney, New South Wales) of Saturday 30^th March 1946:

Air Force and Army slang has become so well known throughout the war years that it now forms part of our civilian speech.
Air Force words and phrases like “doover,” “gremlin,” “gone in,” and “tear a strip off him,” and Army phrases like “gone through on the Padre’s bike,” and “shot through like a Bondi tram” are in constant use.

The phrase gone on the padre’s bike may have originated in a story such as the following, published in the A.I.F. section of Smith’s Weekly (Sydney, New South Wales) of Saturday 25^th August 1934:

The Padre’s Bike

The old Digger spirit of comradeship still lives. Padre Dobbinson, well known in N.S. Wales and Victoria, by Brass Hats ² and Diggers alike, settled in Launceston a couple of years ago, and was gladly welcomed by all ex-A.I.F. men.
Diggers don’t forget the battles he fought in the early 20’s to establish the League and forward its claims on behalf of our less fortunate mates.
A little time ago some “bird” borrowed the Padre’s bike and forgot to return it. The boys at once clubbed together and presented him with a new one inscribed with one-inch letters, “From Diggers to Padre.”
The presentation was made by the president of the Launceston sub-branch in the Anzac hostel billiard room in the presence of a large crowd of returned men. The president in his remarks referred to the Padre’s splendid work on behalf of returned men generally. The Padre was “stonkered” ³ for a reply.
It is the best-known bike in the city, and the boys have the continual sport of pushing it up a side lane or round the corner and then hearing him roar when he misses it. How like the old days when “What was yours was mine, and mine was yours.” Another little drink of the same spirit won’t do us any harm.—“Rick.”

² So called from the gilt insignia on an officer’s cap, the colloquial term brass hat, which originated in military slang, designates a high-ranking officer in the armed forces.
³ Derived from the noun stonk, which denotes a concentrated artillery bombardment, the verb stonker means to kill, to destroy, to defeat, to put out of action, to outwit.