"I said to him once 'just give me some paperwork, sell my paintings, don't get greedy and everything will work out fine'," Mr Buchanan said.
By 2006, the relationship soured when Mr Buchanan started hearing stories about what the seller had been up to.
Baikie refused to either return Mr Buchanan's paintings - a couple of dozen, according to the artist - or give him the cash from their sale.
Mr Buchanan and Graham Brimble, who had also given the amateur art dealer work to sell, made a complaint to police and in June 2013 he was charged and appeared before the Napier District Court.
After denying the charge, Baikie stood trial in the Auckland District Court this week where Judge Brooke Gibson heard from several witnesses who had seen him selling paintings around the country.
Barbara Stevens, who knew Mr Buchanan well, told the court via audio-visual link from Perth that she was bewildered to see Baikie passing himself off as the artist at a market in Wanaka eight years ago.
She challenged him about his identity but he brazenly stuck to his story.
There were further sightings in Napier, Karamea and Piha.
Because of the lack of documentation the Crown could not prove the extent of Baikie's theft or how much the artwork may have been worth but Mr Buchanan said it was not about the money.
"I don't care about that, eh," he said.
Judge Gibson found 59-year-old Baikie guilty of two charges of theft in a special relationship, and was prepared to sentence him yesterday but his lawyers requested time to prepare an application for a discharge without conviction.
Mr Buchanan considered the likelihood of him getting off without penalty as "unlikely" and described the whole scenario as "just all so pathetically sad".
In the meantime, Mr Buchanan's star had been on the rise, selling work around the globe to celebrities such as former member of The Smiths, Johnny Marr.
He had also recently designed the stained glass windows for Kings College's new chapel.
Outside court, Baikie said the court had been told "bold-arsed lies" and he wished he had given evidence.
He was remanded on bail and will be sentenced next month.