Can anyone help me my mind has gone blank! I realise not every observation has a next step but I feel this one should...I just don't know what? Mind freeze!

9 month old baby waved at his mum before for the first time when she went to leave. We were both surprised as this baby never normally notices his mum has left, never mind waves at her! I'm thinking this needs to be developed on, but not sure how? Or even if I'm right?! Any suggestions? X