Bottom Lane Slot not filled

[Ref in PA]

Last night, GV, 3 man crew. I was the lead ready to administer the first of two free throws and Team B (not shooting) has one girl in the first slot, one girl at mid court and the other three huddled by the coach (no time out had been called - just regular game continuation).

I raised my voice three times over a 15-20 second period "I need a player from Team B to be on the lane!" before I got a player from Team B to respond.

Would you handle the situation differently? Would go ahead and administer the first free throw, knowing Team B would be violating? Would you blow the whistle and issue a delay of game warning? Team B definitely did not respond in a timely manner. They did that one other time in the game only the delay was less, but it still was a delay.

As I said, I waited - I did not want to go looking for trouble, but I definitely would have been justified in taking further action. Just wondering, what would you do?