Try not to beat yourself up...we all have these moments.
Many, many years ago my MIL went to the butchers to buy meat, and left her baby son outside the front in the pram (back in those days people thought nothing of doing this). She was halfway home on the bus before she realized she'd left him there.
What I'm sure was very traumatic at the time has mellowed into a family joke over the years. No one judges her. I am the most absent minded person ever. Even my primary school reports say "She is a dreamer." I live so much in my own head that I am terrified of forgetting my baby. I think we just have to learn from these moments.