The Premiership new boys had been keen to loan out the striker after the arrival of Stefan Maierhofer from Rapid Vienna.
“We weren’t going to let Sam go unless we signed Stefan Maierhofer,” Moxey said in the Birmingham Mail.
“Once that was done, we agreed a deal for Derby to take Sam for the season.
“We had lots of options for Sam but he and the manager were happy for him to go to Derby.
“And with them having done a deal with Middlesbrough for Rob Hulse, we thought it would all go through.
“We had a telephone call at 4.30pm to say Hulse’s proposed move to Middlesbrough had fallen through and therefore they couldn’t guarantee Vokes would be playing.
“So that then set off a mad scramble between three or four clubs interested in taking Sam.
“But with the time against us, and with Sam away on international duty, it all became impossible for us to do a deal.”