Can't find some side missions.

[ImNotGoodWithNames]

I've recently finished the game, and I've noticed there are 2 missions I can't find. The descriptions are:
1: Skags eat EVERYTHING.
2: Every once in a while, a goliath gets a good idea...

I've already gone to the maps and searched for them, but that didn't help. Help would be appreciated. Thank you.

[Waste_of_skin]

Kill skags in Arid Nexus - Badlands and a random one will drop an ECHO recorder.

Same deal for the other mission, but this time it's a goliath in The Fridge. You should see him wandering on the far side of that first open area near the entrance. He doesn't seem to spawn until after you complete Cold Shoulder for Scooter.

Edit:
Oh, and if you're thinking that you're missing any other missions, you can check the Wiki:

http://borderlands.wikia.com/wiki/Borderlands_2_mission_flow

[ImNotGoodWithNames]

Thanks!