The former 500cc world champion filed a lawsuit against the Austin circuit, claiming that it had committed fraud in trying to disregard an agreement him to promote an annual race from 2013-2022.
Dorna admitted its early dealings were conducted with Schwantz, under the belief that he possessed such an agreement in contractual form.
It says however that Schwantz was never able to prove his claims by the deadline Dorna set, leaving it with no alternative than to terminate talks.
In a statement, Dorna said: "Dorna Sports S.L. entered into a Promoters Contract with 3four Texas MGP LLC [Schwantz] in connection with the organisation of a FIM MotoGP Grand Prix at The Circuit of the Americas, Austin, Texas, on February 11th 2011 to be effective from the 2013 season.
"Dorna understood that 3four Texas MGP LLC had an agreement with COTA to run the event.
"On the first days of June 2012, Dorna required 3four Texas MGP LLC to provide satisfactory evidence before June 28th about the company having obtained all the necessary rights, licenses and permits related with the availability of the Circuit of the Americas.
"This is a standard procedure when the promoter is not the owner of the circuit.
"3four Texas MGP LLC was not able to provide such evidence to Dorna (apparently no agreement had ever been entered into between 3four Texas MGP LLC and COTA, the owner of the circuit) within the term granted for such purposes, and therefore Dorna had no other alternative than to terminate the February 11th 2011 Promoters Contract due to such event of default.
"The termination was effective from July 2nd 2012.
"As Dorna Sports S.L. and the FIM are interested in a FIM MotoGP Grand Prix in Texas, COTA was then offered the opportunity to become the Promoter of such an event through the signing of a Promoters Agreement.
"Conversations continue at this moment."
The track is set to host its first Formula 1 race in November this year.