When I took my eyes off her for just a minute with 目を離す

Idiom Explanation: Averting one's attention with 目を離す

Satsuki leaves Sara, the young girl she’s watching, alone to go heat up lunch. When she returns with the food, Sara is nowhere to be found. Satsuki calls her sister to let her know what’s happened.

皐(さつき):: 「それが…　ちょっと目(め)を離(はな)した隙(すき)に…」; “The thing is, I took my eyes off her for a just a minute...”; 「これから警察(けいさつ)に連絡(れんらく)して探(さが)しに出(で)るから…」; “I'm going to call the police, then I'm heading out to look for her...”

Key Points

1目(め)を離(はな)した means took my eyes off

目(め)を離(はな)す is an idiom for looking away or stopping watch for a moment.
Satsuki is not literally moving her eyes away as objects; she stopped paying visual attention to Sara.

2ちょっと softens the length of time

ちょっと makes the lapse sound brief, like “just for a bit”.

3隙(すき)に marks the vulnerable moment

隙(すき) is a gap or unguarded opening.
目(め)を離(はな)した隙(すき)に means “in the brief moment when I took my eyes off her”.

4The trailing から explains what Satsuki will do next

The final から after 出(で)る leaves the reason or explanation hanging.
It sounds like she is explaining the situation quickly while already preparing to call the police and search.