Sky News reported on Wednesday that Jo Bamford, a member of the industrial dynasty behind JCB, had entered into exclusive talks to buy the company from administrator Deloitte.
However, by Thursday morning, Jeff Wright - who owns the factory premises - said it was "deeply regrettable" that a deal had not been agreed.
Despite looking all but dead, officials from the Unite union have told Wrightbus workers that talks between the Wright and Bamford camps are ongoing.
The Union says that Mr Bamford is still considering his position.
The move by Mr Bamford, who was among the bidders for Wrightbus before it plunged into insolvency proceedings threatening 1,300 jobs, had raised hopes that the company had a viable future.
Negotiations over rental payments were among the major sticking points that prevented a deal being reached before Wrightbus called in administrators, Sky News understands.
"There's no second chances here - you can't do this again on Friday or Saturday - this is the decision day," North Antrim MP Ian Paisley told BBC Radio Ulster.
Describing Mr Paisley's interventions as "unhelpful to say the least", Mr Wright hit out at the role played by the politician.
"Mr Paisley would be well advised to leave the business of dealmaking to the professionals at Deloittes," he said.