Hogwarts: I Work as an Auror at the Ministry of Magic

Damocles Belby, the inventor of the Wolfsbane potion, disappeared, and his butler took four days to report the incident. After Aurors William and Tonks took over the investigation, they discovered a strange detail. On the day Mr. Belby disappeared, he actually exchanged ten thousand Galleons into Muggle currency... Why did he do this? Can William and Tonks find out the truth of this matter...