To call in sick means to inform one's employer that one will be absent due to illness, which is what he would do in this scenario.
Context: He was on duty Saturday night, but he would inform his employer that he was too ill to come in and they would have to find someone to take his place.
Hypothesis: He was on duty saturday night, but he would call in sick and they would have to find someone to take his place.

Given this context, determine if the hypothesis is true (Yes, no, or unknown)?