Is the intermediary who testified to the buyer's righteousness—based on his apparent state—and did not take any payment for his mediation, liable for the money that the buyer did not pay to the seller, after the buyer absconded?

What has been mentioned does not make the intermediary a guarantor for the remaining portion of the price. His testimony to the buyer regarding the soundness of the goods, based on what is apparent, is not considered deception or fraud against the seller.