Vernacular ('Slang') Indonesian
It is not uncommon to hear Indonesians use 'ketemu' for 'to meet.'
But 'ketemu' is actually a vernacular form of 'bertemu.'
If you want to say, "I met Anita yesterday" :
You should say, "Saya bertemu Anita kemarin." (correct)
NOT, "Saya ketemu Anita kemarin." (incorrect).