Ego knows the following things:
1) Yondu is motivated purely by profit. Ego pays well and promptly, so when Yondu never shows up with his Terran child, despite having confirmed picking him up, it isn't sudden scruples keeping him away.
2) Presumably, something has happened. The Nova Corps hasn't picked them up, and the Kree still have a bounty out, so the ship hasn't been captured. Ravager ships are death traps, though; in all probability the boy is dead
3) If he's dead, then he wasn't a Celestial, so Yondu's saved him some time, really. The boy's a waste of time, nothing more.
He's wrong on all counts, but it will be nearly three decades before he knows that.
