Ghosted

After how many dates do you think you owe someone an explanation for not wanting to see them anymore? I went on 3 dates with a guy and he seemed really into me but all of a sudden he's not talking to me anymore and I'm so confused. We slept together twice so I kind of feel like he should say something to me rather than just dissapearing, and last time I saw him he said he'd text me to go for a drink again some time that week. Have you ever been ghosted? I'm just so confuuuseddddd