The Mariners were told the Welsh winger was not for sale as they attempted to convert his loan switch into a permanent deal at Blundell Park.
Howard Wilkinson clearly feels the former Everton man may not yet be surplus to requirements.
"John Oster is not for sale," insisted Furneaux.
"I was sat next to Bob Murray at the Worthington Cup final and asked him several times about the player.
"I made the enquiry, and asked him again, but he made it absolutely plain that the player was not for sale.
"I think they see him in their plans for the future."
It may be fair to suggest that Wilkinson, despite public comments to the contrary, already has one eye on what is likely to be a Nationwide League promotion challenge next season.
Youngsters such as Matty Piper, Sean Thornton and Michael Proctor could be more influential at a lower level, as should Oster, who has experience of the Nationwide League.
The shape of Wilkinson's team may alter dramatically if the bigger stars, and higher paid individuals, are off-loaded during the summer.
