You discovered that half-orcs had ransacked the vestiges of a camp-site, taking something away with them.
'You say you saw tracks leading southwards? These half-orcs clearly serve Saruman and are bearing their prize to Isengard.
'From what you say, they only have a single horse between them, so it is likely a pack-horse, rather than a mount. You should be able to catch them.
'Fortunately, our scouts saw such a pair of half-orcs to the east and a little south of here, almost due south of the camp-site. Hurry! You must recover whatever they took from the camp-site.'
The half-orcs were seen to the east and a little south of Echad Eregion, almost due south of the Company's camp-site.
Golgallon told you to hunt down the half-orcs and recover whatever they took from the camp-site.
Golgallon is at Echad Eregion, west and north of where you found Thlûk.
You should return to Golgallon with tidings of your encounter with Thlûk.