Oh dear I forgot my umbrella.
Oh dear I left my umbrella at home.
Which sentence is correct? Answer: both! This morning, by mistake, I didn’t take my umbrella when I walked to the station.
If you look carefully at the top sentences you can see we use the verb ‘to leave’ when we forget something and we mention the place. We use the verb ‘to forget’ when we don’t mention the place. So we cannot say, ‘I forgot my umbrella at home,’ and we cannot say, ‘I left my umbrella.’
But today I was very lucky, there was no rain, so actually I said, “Great, I left my umbrella at home.”