TMZ Sports broke the story ... back in April, one of Owens' old storage units was auctioned off after the company that housed it claimed the Hall of Fame WR stopped making payments to them.

The unit was full of amazing items ... there was a custom bust of TO, old playbooks, autographed helmets and sweet Nike cleats.

But, TO says he was NEVER made aware that the storage company still had his stuff ... and in a federal lawsuit filed this summer in Georgia -- he's claiming Atlanta Peach Movers straight-up stole it.

In the lawsuit, Owens says on July 14, 2014 ... he and the storage company had talks over his unit that left him under the impression all of his stuff had been returned to him.

He alleges he has written proof from the company that says his debt was all paid off and his items were out of the unit and back in his possession.

But, he's claiming the company lied to him on purpose in order to steal his stuff and eventually sell it at auction this past spring.

In fact, Owens claims the first time he had heard the company still had his gear was when we reached out to him for our story back in April.

Owens is now suing the company for fraud and breach of contract -- among other things -- claiming he had over $1 MILLION worth of items in that storage unit.

Owens wants to be compensated for the loss of his stuff ... which he claims is "unique, irreplaceable, and priceless."

The man who bought the unit at auction, James Rice of Jan's Used Furniture in Griffin, GA, told us back in April he was willing to give the stuff back to Owens -- but, clearly, that hasn't happened.