Last Rare mob in map impossible to reach

Map Details:
-Oasis Map w/ Tier 3 Waystone
-Mob types: Act 2 mobs

Scenario:
Cleared the map (6 mobs remaining) and caught a glimpse of the last remaining Rare mob, one of the large bugs that fly in from off screen. Cannot figure out how to activate/attract the mob. Map is horseshoe shaped and the mob is in the middle of the horseshoe. The rare at one point was closer to one side but now seems to have moved to an area that I cannot reach. Killed my map.



URL link to imgur for screenshot.
https://imgur.com/a/N7b8bsa