Costa has not featured for the national team since October due to a string of fitness setbacks, but was set to make his return in this month's matches against Ukraine and Netherlands.
However, the 26-year-old picked up a hamstring injury during Chelsea's 3-2 victory over Hull City on Sunday and has since been replaced by Juanmi.
"He has a muscle tear and wasn't going to play," Del Bosque told Onda Cero. "But the lad wanted to come and be examined by our doctors, to make himself available and so that nobody was suspicious.
"As far as I am concerned he didn't have to come because there is maximum confidence in the player and the logical thing would have been not to come, but he wanted to be with us.
"He says he has bad luck and it seems like someone has jinxed him. That's what people say when they really want to come and I hope he is able to join us again soon."
