Are these happening in real time? Or are they pre-recorded? I was listening to scanner and didn't hear that same transmission on the Live audio feed at same time or at all.
Its also possible the feed you were listening to has multiple channels on it. So while you had your scanner dedicated to 1 thing the feed might have missed it while it was picking up traffic on another channel.
Just a guess, you dont mention the feed in question.
All feeds on Broadcastify have an up to 60 seconds delay due to the time required to run through the net to the servers, then back out to your device of choice to listen to them.