Board Thread:Questions and Answers/@comment-27414435-20170407041023/@comment-27282915-20170407163013

Flarefang Dragon "SD" isn't required to be on the field in order to resolve its ability. It just needs to be on the field long enough to "see" the monster destruction. After that, it doesn't matter what happens to Flarefang.

It's similar to the ruling regarding Justice Envoy, Angel Frill and calling another monster. The Resolution Check takes place after the new monster is placed on the field, so for a split second, the two monsters are on the field at the same time. Angel Frill "sees" this interaction, so even if the Resolution Check immediately removes Angel Frill - via size restriction or space restriction - Angel Frill's ability will still activate even from the drop zone.