The Rocky Pathway (the Pathway Series Book 3) by Hazel Goss
In June 2048, Daniel, aged thirteen, is enjoying a picnic with his family and friends at a Yorkshire tourist attraction called Brimham Rocks. While clambering amongst the rocks he finds a portal to the past and is transported to 1859.
Bewildered and frightened Daniel walks until he sees a light glimmering in a farmhouse. Jo and Mary take him in, and he helps them on the farm but at night he is beset with homesickness. Everything is so different, no television, phones or games machines. Butter and cheese must be made, not bought at a supermarket.
Meanwhile his devastated parents have called the police and the search goes on until it becomes too dark. Daniel is eventually recorded as a missing person.
Xen Baxter, one of the friends at the picnic, knows the secret of the portal but has told no-one. He suspects Daniel has found it by accident but telling his parents would not help because the portal only works one way. There is no hope of Daniel returning to his own time.
The Rocky Pathway is the last in The Pathway Trilogy but can be read and enjoyed without reading the previous books.