Why does my pet sometimes disappear when I didn't ask it to?

Whenever a pet just.. Disappears, it's either stuck behind a non-moving entity or there's a simple bug. A non-moving entity will be something normal players also struggle to go around- like rocks or trees. A good example is when your pet doesn't show in the Egyptian map, in the secret boss's lair. It's gotten stuck behind a pillar and therefore, cannot move.