Place it at the end of a chat-recreation edit, after the WhatsApp message sound and before Olha a Mensagem, so the sequence reads as alert, reaction, then checking what arrived in the thread you are showing on screen.
About this sound
This is a 1.7-second Spanish voice clip of someone exclaiming 'Uf loco si se me re pasó' as if just noticing a miss. It feels sheepish and exasperated, the resigned laugh-at-yourself energy of admitting you let something slide completely unnoticed.