EXCLUSIVE

Tom Brady's Super Bowl 49 jersey was being shopped around to a small group of wealthy collectors who were under the impression it was NOT stolen property ... and the asking price was $75k.

TMZ Sports spoke with multiple people directly connected to the situation. One potential buyer was interested in the jersey but says the seller (who was connected to Mauricio Ortega) "fell down a black hole" and it disappeared from the market about 8 months ago.

We're told Ortega has been selling various sports collectibles for years and would tell clients he obtained the items legally through relationships he built with players, coaches and staffers. He would use the selfies he took with stars like Tom Brady, Bob Kraft and Ben Roethlisberger as a way of unofficially authenticating the goods.

We know what you're thinking ... why would anyone buy a high-priced item without proper documentation?

One high-end collector put it this way ...

Ortega is credible and has had documented locker room access for more than a decade. There would be no reason to suspect he stole anything since no media outlet ever reported it was.

Plus, buyers could do home research -- looking at high resolution pics from the Super Bowl -- and self-authenticate the items based on nicks, scratches and other identifying marks on the gear.