Earlier, when Anatomy blew up, Nick turned into mist and left the building while it was covered in smoke by the explosion on the debris.
Escaping had been very easy.
An immediate escape had been necessary since Nick knew that the Doom Sayer would kill him with its ability otherwise.
Anyone who heard the Doom Sayer speak without any protection would die.
That was why he was so incredibly dangerous.
After Nick had escaped, he had waited in hiding near Ghosty's Lab.
He trusted in Vernon's will to survive.
Most likely, Vernon would quickly try to escape the building if he got a chance.
If he immediately ran out, he might meet with Anatomy's forces along the way, or he would get involved in the fight between the Heroes.
Because of that, he had to wait until the coast was clear.
