On Thursday, Mary Kay Cabot of Cleveland.com cited "more than a half a dozen league sources with inside knowledge of how it all went down" and noted the documents each team had didn't match.
Cabot described the process where the Bengals emailed paperwork to the league five minutes before Tuesday's 4 p.m. ET deadline while the Browns didn't, instead sending it to Cincinnati to then send to the NFL.
According to Cabot, the Bengals didn't see the email until Wednesday because it came from assistant Chris Cooper and not executive vice president Sashi Brown. However, it apparently wouldn't have even mattered considering the language on Cleveland's document was different than Cincinnati's, which would have prevented league approval.
"When the Browns received a copy of the Bengals' document at 3:59 p.m., they realized it was different and called the league to appeal," Cabot wrote. "But it was too late. They had run out of time and the trade fell through."
Cabot provided a number of other details regarding the missed trade opportunity, including the fact Bengals owner Mike Brown was the one spearheading the efforts on Cincinnati's part because of his positive relationship with Browns head coach Hue Jackson and his desire to let McCarron play.
Jackson was the Bengals offensive coordinator before he accepted the Browns position.
Cabot also noted Brown "held firm to his asking price" of a second- and third-round pick even when the Browns thought it was too much. The Browns ultimately called the Bengals at 3:54 p.m. ET to do the trade even though it was apparently "dead" at 3:15 p.m. ET.
However, in the rush to get it done in the waning moments, they "apparently weren't on the same page on the terms and conditions of the trade," Cabot wrote. "Or if they were, the two clubs didn't clearly articulate what they were including in their documents."
Now, McCarron is still on the Bengals behind Andy Dalton, and the winless Browns have their merry-go-round of quarterbacks in DeShone Kizer, Kevin Hogan and Cody Kessler.
McCarron isn't exactly a proven commodity with just 119 passing attempts in his career since Cincinnati selected him in the fifth round of the 2014 draft out of Alabama, but he does have experience working with Jackson.
As for the signal-caller's future, he is a restricted free agent in 2018, per Spotrac, and may eventually find himself in a spot where he can choose the best situation from among multiple suitors if and when he hits the market.
There is plenty of upside there compared to the role of starting quarterback for a Browns franchise that hasn't had a winning record since 2007 and is a mere 4-36 over the last three seasons.