Sala and pilot David Ibbotson remain missing after the Piper Malibu plane carrying them over the English Channel disappeared on January 21, two days after the Argentinian striker completed a club-record £15million move to Cardiff.
"One or two of the strikers we were talking about didn't really want to come in the circumstances," Cardiff manager Warnock said ahead of Saturday's Premier League home game against Bournemouth.
"They didn't want to come in after what's happened. So it's been a very difficult window."
Cardiff did recruit Reading's Leandro Bacuna on Thursday, with the Curacao full-back or midfielder joining for around £3million.
“A few weeks ago, I was made aware of some interest and it has all gone from there. I'm very happy and looking forward to getting started,” Bacuna said.
“Every game I play I give 100%, and I'll be fighting hard to help our team. I've played against the manager and you can see he always wants to win. He is so passionate. It's going to be great to work underneath him and hopefully he will push me on as a player.”
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