Hannah Foster disappeared after a night out with a friend in March 2003
A man felt "physically sick" when he matched a colleague with a description of a man police wanted over the murder of Hannah Foster, a court heard.
James Dennis saw a recording of the BBC Crimewatch programme in March 2003 and called police when he saw similarities with accused Maninder Pal Singh Kohli.
Hannah disappeared in Southampton, Hampshire, on 14 March 2003 on a night out. Her body was found two days later.
Mr Kohli, 40, denies kidnap, false imprisonment, rape and murder.
Hannah, a 17-year-old A-level student, had been walking a short distance from a bus stop to her home in the Portswood area when she vanished.
The defence told the court Mr Dennis had lent the defendant money and had hatched a plot to kidnap Mr Kohli on the night Hannah went missing.
Mr Dennis worked with Kohli delivering sandwiches for Hazelwood Foods in Southampton, the court was told.
Maninder Pal Singh Kohli denies all the charges against him
Mr Dennis, a company supervisor, told the jury at Winchester Crown Court on Monday that the Crimewatch appeal said officers were looking for an Asian man with a white van who travelled to the Portsmouth and Southsea areas.
Mr Dennis said there were similarities as Mr Kohli delivered sandwiches in a white van to Portsmouth, but he did not suspect him.
"The description made me physically sick yet I was in two minds whether to phone the police," he said.
Abbas Lakha QC, defending, accused Mr Dennis of lying and withholding information from the police and the jury.
The court heard that Mr Dennis had loaned or given Mr Kohli £16,000 over a period of about 18 months, which was nearly everything Mr Dennis had earned in that time in his £220-a-week job.
Mr Dennis said he had once lent Mr Kohli £1,000 in one week and the giving of money from savings had put a strain on his marriage to his wife Carole.
During questioning, Mr Lakha said Mr Dennis was "desperate" for the cash and hatched the plot to kidnap Mr Kohli.
Mr Lakha also accused Mr Dennis's wife Carole of having an affair with the defendant and said this was the reason he had handed over the cash, to save the couple from embarrassment.
He said that Mr Dennis was desperate to retrieve the money and with his brother Jonathan, who Mr Dennis admitted in court could be violent, they organised the kidnap.
"You thought you had to act then or you might lose all that money forever."
Mr Dennis replied: "I finally realised I had to lose it (the money) or lose what I had. It was hard, I put my family back together, my home back together, and I got on with my life."
He agreed with Mr Lakha that the police could not understand why the amounts had gone to Mr Kohli and earlier in his evidence he said he gave money to him because he was "an idiot".
But Mr Lakha also said that Mr Dennis knew more about the murder of Hannah than he had told the court or the police.
"You did not suspect him (Mr Kohli) because you knew perfectly well what had happened," said Mr Lakha.
"You knew how Hannah Foster came to be abducted and Mr Kohli was not responsible for it and he was not responsible for killing her."
Mr Dennis replied: "That's a lie."
The trial continues.