Blackburn and Orlando City had found an agreement that would have seen McGuire join Rovers on loan.
But a move fell through due to an 'administrative error', the club said in a statement, which turned out to be quite the error.
According to The Athletic, Blackburn thought they had clicked 'submit paperwork' on the English Football League's transfer system before the deadline hit.
However, the club had actually only hit the option to save, meaning the wrong button was pressed.
The Championship side appealed to the EFL but it was rejected, which meant that McGuire was sent back to Orlando after the transfer was cancelled.
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A statement from Blackburn read: "Despite all relevant paperwork being completed and uploaded onto the system in good time, the signed registration documents were not submitted prior to the 11pm deadline.
"At a meeting held earlier today, the EFL Board has upheld the decision of the EFL Executive to reject Rovers' application to register the USA international.
"Upon comprehensive review of submissions, the EFL Board determined that the upload of documents into a draft application area did not constitute sending documents to the EFL.
"It also took the decision that it was not prepared to exercise discretion to permit the registration outside of the window, as the EFL Executive had correctly interpreted and applied its Regulations and associated Guidance.
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"The club is disappointed by the outcome, but accepts the decision of the EFL Board."
McGuire was initially set to join on loan with an option to buy in the final throes of the January transfer window but a deal was cancelled with the striker mid-flight.
Negotiations reopened over a straight loan with hours left in the window before the huge error capsized any chance of a move going through.
The failed move has also had a massive impact on McGuire with Orlando City already signing his replacement in former Atalanta star Luis Muriel.
As for Blackburn, they have been in the news recently with Jon Dahl Tomasson set to leave and replaced by John Eustace.