The Huddersfield striker spent the first half of the campaign on loan with Wigan Athletic, scoring six goals in 16 matches.
Despite him being keen to stay at the DW, Hiwula was recalled by the Terriers during January - although he failed to break back into the first team.
Hiwula has now joined one of Wigan’s biggest rivals for promotion, Walsall, although Caldwell as no hard feelings about the way things have turned out.
“It was one that was out of control - and also out of Jordy’s control!” said the Latics boss.
“Jordy would tell you himself that he loved it here and he wanted to stay.
“For some crazy reason, Huddersfield called him back - and he had to go back and play for their reserve team.
“Thankfully for him, because he is a great lad and very good player, he’s been allowed to go back out on loan to play some football, because he’s another one with a good career in front of him.”
Latics moved swiftly to replace Hiwula with Conor McAleny, meaning a return to the DW was never an option.
“It was something we discussed, but obviously Conor has come in and done extremely well,” Caldwell added.
“The timing would have been wrong, but I’m just happy for Jordy because he’s a player who just wants to play football.”