However team owner Roger Penske has made it clear that that he would be open to working with Allmendinger again in the future, and even made a point of inviting Allmendinger to Fontana for last weekend's IZOD IndyCar Series finale where the team had been hoping to win the championship with driver Will Power, only to be foiled on the last lap by Ryan Hunter-Reay.
"I told AJ I wanted him to come to a race," said Penske on Saturday. "I thought it would be good for him to get out and see people here, talk to some of the team owners.
"He's certainly an option for people on the NASCAR side and the Indy side, he did a great job when you think about what he did in Champ Car," Penske added. "He could be an option for us, for sure."
"He's been amazing and such a great friend through this," said Allmendinger of his relationship with Roger Penske. "He's the guy I always wanted to please and my biggest regret is letting him down."
Fontana marked the first time that Allmendinger had broken cover and been back at a motor race since the furore over the drugs test erupted.
"I'm just happy to be back at a racetrack," said Allmendinger at the weekend. "At this point, I'm keeping all my options open for the future, and I'm open to racing anything," he added, which he reiterated when speaking to reporters on Tuesday after the announcement of his reinstatement.
"The first thing is what options are out there for me? I don't know the answer to that," he told The Associated Press
on Tuesday, saying that he wasn't necessarily favouring either NASCAR or IndyCar at this point even though he still felt that he had "unfinished business" in stock car. "I definitely don't want to go out like that," he added.
As well as Penske, Allmendinger also has a possible way forward with Michael Shank, either in the MSR Indy team that the two of them are partners in, or in Shank's GRAND-AM team which won the Rolex 24 Hours at Daytona in January with Allmendinger among the driver line-up.
Allmendinger's suspension from NASCAR competition covered GRAND-AM, and while it did not technically cover the IndyCar series the organisers of the open wheel championship had made it clear that they would not be happy to certify a driver to race if they were subject to disciplinary action or suspension in another competition.
That made Allmendinger's successful completion of the Road to Recovery program and formal reinstatement a necessity for the driver if he was to have any future in US motorsport. Now that this has happened - and remarkably quickly at that - the future is a lot brighter for the 30-year-old Californian.