Ern was quite aware of the Ron Weasley debacle as it happened that at that very moment he had finished what needed to be done that morning and was heading over to see whether he could have a casual word with one of the Aurors on their most recent cases.
It was rather difficult to miss the huge blow-up doll on Weasley's desk. Feeling as horrified as Ron looked, Ern pretended to look at his watch in surprise and hurry off to an imaginary meeting. Perhaps that's what earned him his nickname from Zacharias... Even if it were an absolute lie.
The second time around, Ern had made a point of just checking to ensure that there was no blow-up doll on the desk. Just as he arrived, he noticed Pucey was approaching. "Pucey, can I have a quick word? It's about the cases."