Her fellow workers thought she had been scrapped half a century ago, but the gallant little engine which shunted wagons at a West chocolate factory has returned home to a hero's reception.

The steam locomotive, built by Sentinel of Shrewsbury in 1928, worked on the internal railway at Fry's Somerdale factory in Keynsham from new for 28 years but was finally sold for scrap in 1964.

Workers at the factory, run by Cadbury, thought they would never see it again but remarkable detective work by local historian and former Somerdale employee Eric Miles, 75, of Kingswood, led him to a Nissan hut in a garden in Essex. The engine had lain there for 19 years, and trees had grown up around it.

Owner Steve Woods said he would like to see the engine go to a preservation society for restoration, and Mr Miles contacted the Avon Valley Railway at Bitton – only a short distance from the Somerdale factory – who enthusiastically offered it a home.

Mr Miles then contacted management at Cadbury's Somerdale who agreed to cover the cost of the engine's purchase and transport as part of their ongoing commitment to the community.

She arrived in the West on a low loader on Saturday, and paid a poignant visit to her old workplace before being finally off-loaded at Bitton Station yesterday.

A delighted Mr Miles, who used to "sneak" rides on the loco as a young man said: "It's great to see her back. When I started to write the book Somerdale Story 1921 – 2009, I began to investigate what had happened to her. All information I received was suggesting that she had been scrapped and parts used for a Sentinel steam wagon, but after three years' hard work I eventually tracked her down to the Nissan hut in Essex."

Mr Miles tracked the engine's movements from its sale to a Bristol scrapyard through two subsequent owners. The only clue to her next owner was a picture of her being lifted by crane onto a low-loader. Mr Miles spotted the name of the crane company in the photograph and contacted the owner of the firm who knew exactly where he had delivered the engine. The search was over.

Now a survey will be undertaken to establish the extent of the restoration required to return the locomotive to steam.